Multi-feature polyaxial screw

ABSTRACT

Bone anchor assemblies are disclosed herein that provide for a single bone anchor assembly that can be utilized across a range of spinal surgical procedures, reduce manufacturing burden and cost, and provide for greater flexibility during a surgical procedure. The bone anchor assemblies disclosed herein include an implantable shank and a receiver member having two spaced apart arms which form a U-shaped seat to receive a rod, among other components. The bone anchor assemblies disclosed herein also provide a number of features to enhance capability and usability. Examples include features to facilitate better implantation of the shank, better coupling of instrumentation to the anchor, better performance in reducing a spinal fixation element, such as a rod, into the receiver member seat, and others.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No.63/157,362, filed on Mar. 5, 2021. This application also claims thebenefit of U.S. Provisional Application No. 63/221,359, filed on Jul.13, 2021. The entire contents of these applications are herebyincorporated by reference in their entirety.

FIELD

This disclosure relates generally to improved polyaxial bone anchorassemblies, which can include a plurality of features, e.g., foroptimized or improved engagement with surgical instruments, surgicalinstrumentation, and/or bone, applicable for use in at leastthoracolumbar spinal applications.

BACKGROUND

Bone anchor assemblies can be used in orthopedic surgery to fix boneduring healing, fusion, or other processes. In spinal surgery, forexample, bone anchor assemblies can be used to secure a rod or otherspinal fixation element to one or more vertebrae to rigidly ordynamically stabilize the spine. Bone anchor assemblies typicallyinclude a bone screw with a threaded shank that is adapted to bethreaded into a vertebra, and a rod-receiving element, usually in theform of a U-shaped slot formed in the head. The shank and rod-receivingassembly can be provided as a monoaxial screw, whereby the rod-receivingelement is fixed with respect to the shank, or a polyaxial screw,whereby the rod-receiving element has free angular movement with respectto the shank. In use, the shank portion of each screw is threaded into avertebra, and once properly positioned, a fixation rod is seated intothe rod-receiving element of each screw. The rod is then locked in placeby tightening a set-screw, plug, or similar type of fastening mechanisminto the rod-receiving element.

With prior bone anchor assemblies, there are a large variety of anchorssuited for specific uses and this can make it difficult for a user toselect the proper anchor, and for suppliers to manufacture and maintaininventories. Further, with prior anchors there are many ways in whichuse can be challenging, such as when implanting an anchor, when couplinginstrumentation to an anchor, when reducing a spinal fixation elementtoward an anchor, etc.

Accordingly, there is a need for improved bone anchor assemblies,particularly assemblies that can be used across a wide variety ofsituations and provide solutions to various usability challenges.

SUMMARY

The bone anchor assemblies disclosed herein, and methods related to thesame, provide for a single bone anchor assembly that can be utilizedacross a range of spinal surgical procedures, reduce manufacturingburden and cost, and provide for greater flexibility during a surgicalprocedure. The bone anchor assemblies disclosed herein include animplantable shank and a receiver member having two spaced apart armswhich form a U-shaped seat to receive a rod, among other components. Thebone anchor assemblies disclosed herein also provide a number offeatures to enhance capability and usability. These include, forexample, features to facilitate better implantation of the shank, bettercoupling of instrumentation to the anchor, better performance inreducing a spinal fixation element, such as a rod, into the receivermember seat, and others.

In one aspect, a bone anchor assembly is disclosed that includes a boneanchor having a proximal head portion and a distal threadedbone-engaging portion. The bone anchor further includes a receivermember having a proximal end defined by a pair of spaced apart armsforming a U-shaped recess therebetween, a distal end having a polyaxialseat formed therein for polyaxially seating the head portion of the boneanchor, a groove formed in an outer surface of each of the spaced apartarms at a proximal end thereof, a first recess formed in the outersurface of each arm with at least a portion of the first recessintersecting the groove, and a second recess formed in an outer surfaceof the receiver member at a position distal to the first recesses.Moreover, the first recesses and the second recesses are configured tocouple to a surgical instrument.

Any of a variety of alternative or additional features can be includedand are considered within the scope of the present disclosure. Forexample, in some embodiments, at least a portion of the first recess ineach arm can extend proximally beyond the groove. In certainembodiments, each of the second recesses can be longitudinally alignedwith one of the first recesses. In some embodiments, the first recessescan be configured to pivotably couple to a surgical instrument. Incertain embodiments, the pair of second recesses can be configured topivotably couple to a surgical instrument.

In some embodiments, the U-shaped recess can be configured to receive aspinal fixation element of various sizes.

In certain embodiments, each spaced apart arm can have alaterally-facing recessed portion formed on opposite lateral edges ofthe arm, each of the lateral-facing recessed portions facing away from acentral proximal-distal axis of the receiver member, wherein thelateral-facing recessed portions can be configured to engage with asurgical instrument such that the U-shaped recess remains unobstructed.In some embodiments, each of the lateral-facing recessed portions canextend distally from the proximal end of the spaced apart arms. Incertain embodiments, each lateral-facing recessed portion can have aconcave distal surface. In some embodiments, each lateral-facingrecessed portion can have a first planar surface, a second planarsurface substantially perpendicular to the first planar surface, and acurved surface therebetween.

In some embodiments, the proximal ends of the spaced apart arms can liealong a common circular circumferential path.

In certain embodiments, opposing laterally-facing sides of the receivermember can taper inward towards the proximal end of the receiver member.In some embodiments, a first pair of opposed sides of the receivermember can have a first taper with respect to a first plane thatcontains a proximal-distal axis of the receiver member. A second pair ofopposed sides of the receiver member can have a second taper withrespect to a second plane that contains the proximal-distal axis and isoffset from the first plane. The first plane can be perpendicular to thesecond plane.

In some embodiments, the assembly can include a drag ring disposedwithin the receiver member, the drag ring can be configured to exert afriction force on the head portion of the bone anchor.

In certain embodiments, the assembly can include a compression memberdisposed within the receiver member, wherein a proximal portion of thecompression member includes opposing planar surfaces that are angularlyoffset from one another forming a seat for receiving a spinal fixationelement. Material displaced in the formation of the second recesses canbe configured to restrict movement of the compression member relative tothe receiver member. The displaced material can be received withincorresponding recesses formed in the compression member.

In some embodiments, the assembly can include a pair of reduction tabsextending proximally from the pair of spaced apart arms.

In certain embodiments, the assembly can include a fixation element withexternal square threads configured to be received between the spacedapart arms of the receiver member.

In some embodiments, the bone anchor can includes a bore extendingproximally from a distal tip of the bone engaging portion. The bore canextend through an entire length of the bone anchor. The bore can be ablind bore.

In some embodiments, the distal bone-engaging portion can includeexternal threads that extend distally along the bone-engaging portion toa distal tip thereof.

In another aspect, a bone anchor assembly is disclosed that includes abone anchor having a proximal head portion and a distal threadedbone-engaging portion. The assembly further includes a receiver memberhaving a proximal end defined by a pair of spaced apart arms forming aU-shaped recess configured to receive a spinal fixation elementtherebetween and a distal end having a polyaxial seat formed therein forpolyaxially seating the head portion of the bone anchor. Moreover,opposing laterally-facing sides of the receiver member taper inwardtowards the proximal end of the receiver member.

As with the assemblies described above, there are a variety ofadditional or alternative features that are considered within the scopeof the present disclosure. For example, in some embodiments a first pairof the opposing laterally-facing sides of the receiver member can have afirst taper with respect to a first plane that contains aproximal-distal axis of the receiver member. A second pair of theopposing laterally-facing sides of the receiver member can have a secondtaper with respect to a second plane that contains the proximal-distalaxis and is offset from the first plane. The first plane can beperpendicular to the second plane.

In some embodiments, the receiver member can include a groove formed inan outer surface of each of the spaced apart arms at a proximal endthereof, a first recess formed in the outer surface of each arm with atleast a portion of the first recess intersecting the groove, and asecond recess formed in an outer surface of the receiver member at aposition distal to the first recesses. The first recesses and the secondrecesses can be configured to couple to a surgical instrument. At leasta portion of the first recess in each arm can extend proximally beyondthe groove. Each of the second recesses can be longitudinally alignedwith one of the first recesses. The first recesses can be configured topivotably couple to a surgical instrument. The pair of second recessescan be configured to pivotably couple to a surgical instrument.

In some embodiments, the U-shaped recess can be configured to receive aspinal fixation element of various sizes.

In certain embodiments, each spaced apart arm can have alaterally-facing recessed portion formed on opposite lateral edges ofthe arm, each of the lateral-facing recessed portions facing away from acentral proximal-distal axis of the receiver member, wherein thelateral-facing recessed portions are configured to engage with asurgical instrument such that the U-shaped recess remains unobstructed.Each of the lateral-facing recessed portions can extend distally fromthe proximal end of the spaced apart arms. Each lateral-facing recessedportion can have a concave distal surface. Each lateral-facing recessedportion can have a first planar surface, a second planar surfacesubstantially perpendicular to the first planar surface, and a curvedsurface therebetween.

In some embodiments, the proximal ends of the spaced apart arms can liealong a common circular circumferential path.

In certain embodiments, the assembly can include a drag ring disposedwithin the receiver member, the drag ring configured to exert a frictionforce on the head portion of the bone anchor.

In some embodiments, the assembly can include a compression memberdisposed within the receiver member, wherein a proximal portion of thecompression member includes opposing planar surfaces that are angularlyoffset from one another forming a seat for receiving a spinal fixationelement. Material displaced in the formation of the second recesses canbe configured to restrict movement of the compression member relative tothe receiver member. The displaced material can be received withincorresponding recesses formed in the compression member.

In certain embodiments, the assembly can include a pair of reductiontabs extending proximally from the pair of spaced apart arms.

In some embodiments, the assembly can include a fixation element withexternal square threads configured to be received between the spacedapart arms of the receiver member.

In certain embodiments, the bone anchor can include a bore extendingproximally from a distal tip of the bone engaging portion. The bore canextend through an entire length of the bone anchor. The bore can be ablind bore.

In some embodiments, the distal bone-engaging portion can includeexternal threads that extend distally along the bone-engaging portion toa distal tip thereof.

In another aspect, a bone anchor assembly is disclosed that includes abone anchor having a proximal head portion and a distal threadedbone-engaging portion. The assembly further includes a receiver memberhaving a proximal end defined by a pair of spaced apart arms forming aU-shaped recess configured to receive a spinal fixation elementtherebetween and a distal end having a polyaxial seat formed therein forpolyaxially seating the head portion of the bone anchor. Moreover,proximal ends of the spaced apart arms lie along a common circularcircumferential path.

Any of a variety of alternative or additional features can be includedand are considered within the scope of the present disclosure. Forexample, in some embodiments, the receiver member can include a grooveformed in an outer surface of each of the spaced apart arms at aproximal end thereof, a first recess formed in the outer surface of eacharm with at least a portion of the first recess intersecting the groove,and a second recess formed in an outer surface of the receiver member ata position distal to the first recesses. The first recesses and thesecond recesses can be configured to couple to a surgical instrument. Atleast a portion of the first recess in each arm can extend proximallybeyond the groove. Each of the second recesses can be longitudinallyaligned with one of the first recesses. The first recesses can beconfigured to pivotably couple to a surgical instrument. The pair ofsecond recesses can be configured to pivotably couple to a surgicalinstrument.

In some embodiments, the U-shaped recess can be configured to receive aspinal fixation element of various sizes.

In certain embodiments, each spaced apart arm can have alaterally-facing recessed portion formed on opposite lateral edges ofthe arm, each of the lateral-facing recessed portions facing away from acentral proximal-distal axis of the receiver member, wherein thelateral-facing recessed portions are configured to engage with asurgical instrument such that the U-shaped recess remains unobstructed.Each of the lateral-facing recessed portions can extend distally fromthe proximal end of the spaced apart arms. Each lateral-facing recessedportion can have a concave distal surface. Each lateral-facing recessedportion can have a first planar surface, a second planar surfacesubstantially perpendicular to the first planar surface, and a curvedsurface therebetween.

In some embodiments, opposing laterally-facing sides of the receivermember can taper inward towards the proximal end of the receiver member.A first pair of opposed sides of the receiver member can have a firsttaper with respect to a first plane that contains a proximal-distal axisof the receiver member. A second pair of opposed sides of the receivermember can have a second taper with respect to a second plane thatcontains the proximal-distal axis and is offset from the first plane.The first plane can be perpendicular to the second plane.

In certain embodiments, the assembly can include a drag ring disposedwithin the receiver member, the drag ring configured to exert a frictionforce on the head portion of the bone anchor.

In some embodiments, the assembly can include a compression memberdisposed within the receiver member, wherein a proximal portion of thecompression member includes opposing planar surfaces that are angularlyoffset from one another forming a seat for receiving a spinal fixationelement. Material displaced in the formation of the second recesses canbe configured to restrict movement of the compression member relative tothe receiver member. The displaced material can be received withincorresponding recesses formed in the compression member.

In certain embodiments, the assembly can include a pair of reductiontabs extending proximally from the pair of spaced apart arms.

In some embodiments, the assembly can include a fixation element withexternal square threads configured to be received between the spacedapart arms of the receiver member.

In certain embodiments, the bone anchor can include a bore extendingproximally from a distal tip of the bone engaging portion. The bore canextend through an entire length of the bone anchor. The bore can be ablind bore.

In some embodiments, the distal bone-engaging portion can includeexternal threads that extend distally along the bone-engaging portion toa distal tip thereof.

In another aspect, a bone anchor assembly is disclosed that includes abone anchor having a proximal head portion, a distal bone-engagingportion with external threads that extend to a distal tip of the boneanchor, and a bore centered within the distal bone-engaging portionextending proximally from the distal tip of the bone anchor. Theassembly further includes a receiver member having a proximal enddefined by a pair of spaced apart arms forming a U-shaped recessconfigured to receive a spinal fixation element therebetween and adistal end having a polyaxial seat formed therein for polyaxiallyseating the head portion of the bone anchor.

Any of a variety of alternative or additional features can be includedand are considered within the scope of the present disclosure. Forexample, in some embodiments, the receiver member can include a grooveformed in an outer surface of each of the spaced apart arms at aproximal end thereof, a first recess formed in the outer surface of eacharm with at least a portion of the first recess intersecting the groove,and a second recess formed in an outer surface of the receiver member ata position distal to the first recesses. The first recesses and thesecond recesses can be configured to couple to a surgical instrument. Atleast a portion of the first recess in each arm can extend proximallybeyond the groove. Each of the second recesses can be longitudinallyaligned with one of the first recesses. The first recesses can beconfigured to pivotably couple to a surgical instrument. The pair ofsecond recesses can be configured to pivotably couple to a surgicalinstrument.

In some embodiments, the U-shaped recess can be configured to receive aspinal fixation element of various sizes.

In certain embodiments, each spaced apart arm can have alaterally-facing recessed portion formed on opposite lateral edges ofthe arm, each of the lateral-facing recessed portions facing away from acentral proximal-distal axis of the receiver member, wherein thelateral-facing recessed portions are configured to engage with asurgical instrument such that the U-shaped recess remains unobstructed.Each of the lateral-facing recessed portions can extend distally fromthe proximal end of the spaced apart arms. Each lateral-facing recessedportion can have a concave distal surface.

In some embodiments, the proximal ends of the spaced apart arms can liealong a common circular circumferential path.

In some embodiments, opposing laterally-facing sides of the receivermember can taper inward towards the proximal end of the receiver member.A first pair of opposed sides of the receiver member can have a firsttaper with respect to a first plane that contains a proximal-distal axisof the receiver member. A second pair of opposed sides of the receivermember can have a second taper with respect to a second plane thatcontains the proximal-distal axis and is offset from the first plane.The first plane can be perpendicular to the second plane.

In certain embodiments, the assembly can include a drag ring disposedwithin the receiver member, the drag ring configured to exert a frictionforce on the head portion of the bone anchor.

In some embodiments, the assembly can include a compression memberdisposed within the receiver member, wherein a proximal portion of thecompression member includes opposing planar surfaces that are angularlyoffset from one another forming a seat for receiving a spinal fixationelement. Material displaced in the formation of the second recesses canbe configured to restrict movement of the compression member relative tothe receiver member. The displaced material can be received withincorresponding recesses formed in the compression member.

In certain embodiments, the assembly can include a pair of reductiontabs extending proximally from the pair of spaced apart arms.

In another aspect, a bone anchor assembly is disclosed that includes abone anchor having a proximal head portion, a distal bone-engagingportion with external threads that extend to a distal tip of boneanchor, and a bore centered within the distal bone-engaging portionextending proximally from the distal tip of the bone anchor. Theassembly also includes a receiver member having a proximal end definedby a pair of spaced apart arms forming a U-shaped recess therebetween, adistal end having a polyaxial seat formed therein for polyaxiallyseating the head portion of the bone anchor, a groove formed in an outersurface of each of the spaced apart arms at a proximal end thereof, afirst recess formed in the outer surface of each arm with at least aportion of the first recess intersecting the groove, and a second recessformed in an outer surface of the receiver member at a position distalto the first recesses. The assembly further includes a drag ringdisposed within the receiver member, the drag ring configured to exert afriction force on the head portion of the bone anchor. The assemblyfurther includes a compression member disposed within the receivermember, wherein a proximal portion of the compression member includesopposing planar surfaces that are angularly offset from one anotherforming a seat for receiving a spinal fixation element. Moreover, thefirst recesses and the second recesses of the receiver member areconfigured to couple to a surgical instrument. Further, each spacedapart arm has a laterally-facing recessed portion formed on oppositelateral edges of the arm, each of the lateral-facing recessed portionsfacing away from a central proximal-distal axis of the receiver member,wherein the lateral-facing recessed portions are configured to engagewith a surgical instrument such that the U-shaped recess remainsunobstructed. Still further, opposing laterally-facing sides of thereceiver member taper inward towards the proximal end of the receivermember.

Any of a variety of alternative or additional features can be includedand are considered within the scope of the present disclosure. Forexample, in some embodiments, the proximal ends of the spaced apart armscan lie along a common circular circumferential path. And in certainembodiments, the compression member can be locked against removal froman interior of the receiver member.

In another aspect, a bone anchor assembly is disclosed that includes abone anchor having a proximal portion and a distal threadedbone-engaging portion, as well as a locking sphere configured to coupleto the proximal portion of the bone anchor. The assembly furtherincludes a receiver member having a proximal end defined by a pair ofspaced apart arms forming a U-shaped recess therebetween, and a distalend having a polyaxial seat formed therein for polyaxially seating thelocking sphere, as well as a drag ring disposed within the receivermember and configured to exert a friction force on the locking sphere,and a compression member disposed within the receiver member. Moreover,a distal facing surface of the receiver member is obliquely angledrelative to a central proximal-distal axis of the receiver member toprovide a greater degree of angulation of the bone anchor relative tothe receiver member in a first direction relative to a second, oppositedirection.

Any of a variety of alternative or additional features can be includedand are considered within the scope of the present disclosure. Forexample, in some embodiments, the receiver member can include a grooveformed in an outer surface of each of the spaced apart arms at aproximal end thereof. Further, the receiver member can include a firstrecess formed in the outer surface of each arm with at least a portionof the first recess intersecting the groove, and a second recess formedin an outer surface of the receiver member at a position distal to thefirst recesses. Moreover, the first and second recesses can beconfigured to couple to a surgical instrument. In some embodiments, Atleast a portion of the first recess in each arm extends proximallybeyond the groove. The second recess can be longitudinally aligned withone of the first recesses. The first recesses can be configured topivotably couple to a surgical instrument. The second recess can beconfigured to pivotably couple to a surgical instrument as well.

In certain embodiments, the U-shaped recess can be configured to receivea spinal fixation element of various sizes.

In some embodiments, each spaced apart arm can have a laterally-facingrecessed portion formed on opposite lateral edges of the arm, each ofthe lateral-facing recessed portions facing away from the centralproximal-distal axis of the receiver member, wherein the lateral-facingrecessed portions are configured to engage with a surgical instrumentsuch that the U-shaped recess remains unobstructed. Each of thelateral-facing recessed portions can extend distally from the proximalend of the spaced apart arms. Each lateral-facing recessed portion canhave a concave distal surface. Each lateral-facing recessed portion canhave a first planar surface, a second planar surface substantiallyperpendicular to the first planar surface, and a curved surfacetherebetween.

In certain embodiments, the proximal ends of the spaced apart arms canlie along a common circular circumferential path.

In some embodiments, opposing laterally-facing sides of the receivermember can taper inward towards the proximal end of the receiver member.A first pair of opposed sides of the receiver member can have a firsttaper with respect to a first plane that contains a proximal-distal axisof the receiver member. A second pair of opposed sides of the receivermember can have a second taper with respect to a second plane thatcontains the proximal-distal axis and is offset from the first plane.The first plane can be perpendicular to the second plane.

In certain embodiments, a proximal portion of the compression member caninclude opposing planar surfaces that are angularly offset from oneanother forming a seat for receiving a spinal fixation element. Materialdisplaced in the formation of the second recess can be configured torestrict movement of the compression member relative to the receivermember. The displaced material can be received within a correspondingrecess formed in the compression member.

In some embodiments, the assembly can include a pair of reduction tabsextending proximally from the pair of spaced apart arms.

In certain embodiments, the assembly can include a fixation element withexternal square threads configured to be received between the spacedapart arms of the receiver member.

In some embodiments, the bone anchor can include a bore extendingproximally from a distal tip of the bone engaging portion. The bore canextend through an entire length of the bone anchor. The bone anchor caninclude at least one outlet formed in a lateral surface thereof thatintersects with the bore. The bore can be a blind bore.

In certain embodiments, the distal bone-engaging portion can includeexternal threads that extend distally along the bone-engaging portion toa distal tip thereof.

In some embodiments, the compression member can be configured to exert aforce on the locking sphere upon distal advancement of the compressionmember relative to the receiver member.

In certain embodiments, the bone anchor can include threads of a firstpitch formed along a first bone-engaging portion thereof and threads ofa second pitch formed along a second bone-engaging portion that isproximal of the first bone engaging portion. The first pitch can begreater than the second pitch.

In some embodiments, the bone anchor can include threads formed on afirst, distal portion thereof and a second portion without threads thatis disposed between the first portion and the proximal portion of thebone anchor. Moreover, a length of the second portion without threadscan be at least about 30% of a length of the first portion havingthreads formed thereon. The length of the second portion can also bebetween about 30% and about 90% of the length of the first portion.

Any of the features or variations described herein can be applied to anyparticular aspect or embodiment of the present disclosure in a number ofdifferent combinations. The absence of explicit recitation of anyparticular combination is due solely to avoiding unnecessary length orrepetition.

BRIEF DESCRIPTION OF THE DRAWINGS

The aspects and embodiments of the present disclosure can be more fullyunderstood from the following detailed description taken in conjunctionwith the accompanying drawings, in which:

FIG. 1 is a perspective view of a bone anchor assembly, according to oneembodiment;

FIG. 2 is a cross-sectional view of the bone anchor assembly of FIG. 1;

FIG. 3 is an enlarged cross-sectional view of a proximal portion of thebone anchor assembly of FIG. 1;

FIG. 4 is an enlarged prospective view of the proximal portion of thebone anchor assembly of FIG. 1;

FIG. 5 is a side view of one embodiment of a bone anchor assembly;

FIG. 6 is a partially transparent front view of the proximal portion ofthe bone anchor assembly of FIG. 1;

FIG. 7 is a partially transparent side view of the proximal portion ofthe bone anchor assembly of FIG. 1 in an orientation that is 90 degreesoffset from the orientation shown in FIG. 6;

FIG. 8 is a front view of the proximal portion of the bone anchorassembly of FIG. 1 in the orientation shown in FIG. 6;

FIG. 9 is a side view of the bone anchor assembly of FIG. 1 in theorientations shown in FIG. 7;

FIG. 10 is a perspective view of a compression cap, according to oneembodiment;

FIG. 11 is a front view of the compression cap of FIG. 10;

FIG. 12 is a front cross-sectional view of the compression cap as shownin FIG. 11;

FIG. 13A is a perspective view of the bone anchor assembly of FIG. 1;

FIG. 13B is a proximal end perspective view of the shank of the boneanchor assembly of FIG. 1;

FIG. 13C is a detail perspective view of the distal end of the shank ofthe bone anchor assembly of FIG. 1;

FIG. 13D is a partially-transparent view of FIG. 13C;

FIG. 14 is a perspective view of a set screw, according to oneembodiment;

FIG. 15A is an illustration of reducer instrument being introduced to abone anchor assembly;

FIG. 15B is an illustration of a reducer instrument holding a rod in abone anchor assembly and introducing a set screw to lock a position ofthe rod;

FIG. 16 is a top view of the bone anchor assembly of FIG. 1;

FIG. 17 is a perspective cross-sectional view bisecting the receivermember of the bone anchor assembly of FIG. 1;

FIG. 18 is a detail perspective view of a proximal portion of thereceiver member of the bone anchor assembly of FIG. 1;

FIG. 19 is an exploded view of the bone anchor assembly of FIG. 1;

FIG. 20 is a perspective view of a bone anchor assembly, according toone embodiment;

FIG. 21 is another perspective view of the bone anchor assembly of FIG.20;

FIG. 22 is an exploded view of the bone anchor assembly of FIG. 20;

FIG. 23 is a perspective longitudinal cross-sectional view of the boneanchor assembly of FIG. 20;

FIG. 24 is an enlarged partially transparent perspective view of theproximal portion of the bone anchor assembly of FIG. 20;

FIG. 25 is a front view of the proximal portion of the bone anchorassembly of FIG. 20;

FIG. 26 is a front cross-sectional view of the proximal portion of thebone anchor assembly of FIG. 20;

FIG. 27 is a side view of the proximal portion of the bone anchorassembly of FIG. 20;

FIG. 28 is an opposing side view of FIG. 27;

FIG. 29 is a top view of the bone anchor assembly of FIG. 20;

FIG. 30 is a bottom view of the bone anchor assembly of FIG. 20;

FIG. 31 is a perspective partial cross-sectional view bisecting thereceiver member of the bone anchor assembly of FIG. 20;

FIG. 32 is an enlarged perspective view of the proximal portion of thereceiver member of the bone anchor assembly of FIG. 20;

FIG. 33 is a partially transparent side view of the proximal portion ofthe receiver member of the bone anchor assembly of FIG. 20;

FIG. 34A is a perspective view of a bone shank of the bone anchorassembly of FIG. 20;

FIG. 34B is a partially transparent view of FIG. 34A;

FIG. 35 is a perspective view of a receiver member of the bone anchorassembly of FIG. 20;

FIG. 36 is a front view of the receiver member of FIG. 35;

FIG. 37 is a top view of the receiver member of FIG. 35;

FIG. 38 is a bottom view of the receiver member of FIG. 35;

FIG. 39 is a perspective view of a locking sphere of the bone anchorassembly of FIG. 20;

FIG. 40 is a perspective cross-sectional view of the locking sphere ofFIG. 39;

FIG. 41 is a perspective view of a drag ring of the bone anchor assemblyof FIG. 20;

FIG. 42 is a perspective view of a compression member of the bone anchorassembly of FIG. 20;

FIG. 43 is another perspective view of the compression member of FIG.42;

FIG. 44 is a front view of the compression member of FIG. 42;

FIG. 45 is a front cross-sectional view of the compression member ofFIG. 42;

FIG. 46 is a perspective view of a bone anchor assembly, according toone embodiment;

FIG. 47 is another perspective view of the bone anchor assembly of FIG.46;

FIG. 48 is an exploded view of the bone anchor assembly of FIG. 46;

FIG. 49 is a perspective longitudinal cross-sectional view of the boneanchor assembly of FIG. 46;

FIG. 50 is a perspective view of a bone anchor assembly, according toone embodiment;

FIG. 51 is another perspective view of the bone anchor assembly of FIG.50;

FIG. 52 is an exploded view of the bone anchor assembly of FIG. 50;

FIG. 53 is a perspective longitudinal cross-sectional view of the boneanchor assembly of FIG. 50;

FIG. 54 is a front view of the bone anchor assembly of FIG. 50 in anangulated state;

FIG. 55 is a front view of a bone anchor assembly, according to oneembodiment;

FIG. 56 is a front view of a bone anchor assembly, according to oneembodiment;

FIG. 57 is a perspective view of a bone anchor assembly, according toone embodiment;

FIG. 58 is another perspective view of the bone anchor assembly of FIG.57;

FIG. 59A is a detail perspective view of a proximal portion of the boneanchor assembly of FIG. 57;

FIG. 59B is a detail front view of a proximal portion of the bone anchorassembly of FIG. 57;

FIG. 60 is a partially-transparent front view of the bone anchorassembly of FIG. 60;

FIG. 61 is an exploded view of the bone anchor assembly of FIG. 57;

FIG. 62 is a front cross-sectional view of the bone anchor assembly ofFIG. 57;

FIG. 63 is a perspective view of a compression member of the bone anchorassembly of FIG. 57;

FIG. 64 is a perspective view of the compression member of FIG. 63;

FIG. 65 is a front view of the compression member of FIG. 63; and

FIG. 66 is a front cross-sectional view of the compression member ofFIG. 63.

DETAILED DESCRIPTION

Certain example embodiments will now be described to provide an overallunderstanding of the principles of the structure, function, manufacture,and use of the devices, systems, and methods disclosed herein. One ormore examples of these embodiments are illustrated in the accompanyingdrawings. The devices, systems, and methods specifically describedherein and illustrated in the accompanying drawings are non-limitingembodiments. The features illustrated or described in connection withone embodiment may be combined with the features of other embodiments.Such modifications and variations are intended to be included within thescope of the present disclosure. Additionally, to the extent thatlinear, circular, or other dimensions are used in the description of thedisclosed devices and methods, such dimensions are not intended to limitthe types of shapes that can be used in conjunction with such devicesand methods. Equivalents to such dimensions can be determined fordifferent geometric shapes, etc. Further, like-numbered components ofthe embodiments can generally have similar features. Still further,sizes and shapes of the devices, and the components thereof, can dependat least on the anatomy of the subject in which the devices will beused, the size and shape of objects with which the devices will be used,and the methods and procedures in which the devices will be used.

The bone anchor assemblies disclosed herein, and methods related to thesame, provide for a single bone anchor assembly that can be utilizedacross a range of spinal surgical procedures, reduce manufacturingburden and cost, and provide for greater flexibility during a surgicalprocedure. The bone anchor assemblies disclosed herein include animplantable shank and a receiver member having two spaced apart armswhich form a U-shaped seat to receive a rod, among other components. Thebone anchor assemblies disclosed herein also provide a number offeatures to enhance capability and usability. These include, forexample, features to facilitate better implantation of the shank, bettercoupling of instrumentation to the anchor, better performance inreducing a spinal fixation element, such as a rod, into the receivermember seat, and others.

FIG. 1 illustrates a perspective view of one embodiment of a bone anchorassembly 100 of the present disclosure. The bone anchor assembly caninclude a receiver member 102 and a bone shank 104 having a proximalhead portion 106 and a distal bone-engaging portion 108. The receivermember 102 can have a proximal portion 110 defined by a pair of spacedapart arms 112 and 114 forming a U-shaped recess 119 (also referred toas a rod-receiving recess or slot) therebetween to receive a spinalfixation element (not shown), such as a spinal rod. A polyaxial seat 608(see FIG. 6) is formed in a distal end 120 of the receiver member 102for polyaxially seating the head portion 302 (shown in FIG. 2 and FIG.3) of the bone shank 104. As discussed in detail below, the receivermember 102 can have multiple distinct engagement or attachment featuresto facilitate coupling of the receiver member 102 to surgicalinstruments during use. FIG. 2 is a cross-sectional view of the boneanchor assembly 100 of FIG. 1, and FIG. 3 is an enlarged cross-sectionalview of the receiver member 102. As shown in FIG. 2, the bone anchorassembly 100 can further include a compression cap 202 and a drag ring204 disposed within the distal end 120 of the receiver member 102. Thecompression cap 202 and drag ring 204 can contact the proximal head 302of the shank 104. FIG. 3 illustrates that the proximal head 302 of theshank 104 seated in the distal end 120 of the receiver member 102.

FIG. 4 is an enlarged perspective partial view of the bone anchorassembly 100 of FIG. 1, highlighting particular elements or features ofthe receiver member 102 that are discussed in detail below. Receivermembers of the present disclosure can include any of the featuresdiscussed herein, taken alone or in combination with one another. Forexample, the receiver member 102 can include one or more features tofacilitate engagement of a surgical instrument with the bone anchorassembly 100. A groove or a channel 402 can be formed in an outersurface at the proximal end 112′, 114′ of each of the spaced apart arms112, 114. The groove or channel 402 can define a “top-notch” featurethat can be engaged with a corresponding portion of an instrument, suchas a projection, to facilitate coupling of the instrument to thereceiver member 102. Additional details regarding such a feature can befound in U.S. Pat. Nos. 10,039,578 and 10,299,839, the entire contentsof which are incorporated by reference herein.

FIG. 4 also shows a proximal rocker feature (also referred to as a firstrecess) 404 formed in the proximal portion 110 of the receiver member102 that can be used to facilitate reducing a rod (not shown) distallyinto the U-shaped recess 119 of the receiver member 102. The proximalrocker reducer feature 404 can allow a rocker instrument to pivotablycouple to the receiver member 102 for reduction of a spinal fixationelement in the receiver member 102 using a levering or rocking motion.The proximal rocker feature 404 can be a bilateral circular detail orrecess that intersects the top-notch feature 402, described above. Inother words, each of the spaced apart arms 112, 114 can include aproximal rocker feature 404 that intersects with the groove or channel402 formed at a proximal end 112′, 114′ of the arm 112, 114. A portionof the proximal rocker feature 404 can extend proximally of the groove402, intersecting material of the spaced apart arms 112, 114 above thegroove 402 (see FIG. 9). This can provide stronger contact between thereceiver member 102 and a surgical instrument, and reduce variability inmanufacturing of the receiver members.

Additionally or alternatively, the receiver member 102 can include adistal rocker feature (also referred to as a second recess) 406. Thedistal rocker feature 406 can be formed in the receiver member 102 at aposition distal to the proximal rocker feature 404. The second rockerfeature 406 can provide an alternative coupling position for a rockerinstrument, such as a reducer rocker fork, to the proximal/first rockerfeature 404. The second rocker feature 406 can also be a swage featureused to retain a compression cap 202 within the receiver member 102.During assembly, for example, a swaging process can form the secondrocker feature 406 and displace receiver member 102 material into arecess 304 formed in the compression cap (also referred to as acompression member) (see FIG. 3) to constrain the compression cap 202within the receiver member 102 and prevent, e.g., its removal out theproximal end 110 of the receiver member 102. The second rocker feature406 can be formed on opposing sides of the receiver member 102 andmaterial in each arm 112, 114 of the receiver member 102 can bedisplaced by swaging into the recesses 304 formed on opposing sides ofthe compression cap 202. This material displacement into the compressioncap 202 can assist in holding the bone anchor assembly 100 together andprevent disassembly of the compression cap 202, bone anchor shank 104,and receiver member 102.

As shown in FIG. 4, the receiver member 102 can include at least oneunilateral attachment feature 408 that can enable a surgical instrumentto couple to or engage with the receiver member 102 in a manner thatleaves the rod-receiving slot 119 unobstructed, e.g., by allowingattachment of an instrument to the receiver member 102 by engaging onlyone arm 112, 114 of the receiver member 102. In one embodiment, thereceiver member 102 can include a unilateral attachment feature 408 onfour proximal quadrants of the receiver member 102. For example, aunilateral attachment feature can be formed on opposing laterally-facingedges of each of the spaced apart arms 112, 114. A surgical instrumentcan attach to two adjacent unilateral features 408 on one side of thereceiver member 102, leaving the rod-receiving slot 119 open to receivea spinal fixation rod and/or set screw introduced distally from theproximal end 110 of the receiver member 102. This can allow formanipulation of the receiver member 102, attachment of a reductioninstrument, and/or insertion of a spinal fixation element or lockingelement into the rod-receiving slot 119. As shown in FIGS. 4 and 17,each lateral-facing recessed portion 408 can have a concave distalsurface 409. In some embodiments, such as that shown in FIG. 59, eachunilateral attachment feature 408 can have a planar distal surface 5711having approximately a 90 degree angle with a sidewall surface 5713,with a concave surface therebetween having a smaller radius than thesurface 409. Such a configuration can provide additional planar bracingsurfaces for use when coupling with an instrument Additional detailspertaining to unilateral attachment feature(s) can be found in U.S.Patent Application Publication No. 2019/0183541, entitled “UnilateralImplant Holders and Related Methods,” the entire contents of which areincorporated by reference herein.

As indicated in FIG. 4 and discussed in detail below with respect toFIGS. 10-12, the receiver member 102 can receive spinal fixationelements of multiple sizes. For example, spinal rods having a diameterof about 5.5 mm or a diameter of about 6.0 mm can be received within therod-receiving recess 119. A proximal portion of the spaced apart arms112, 114 of the receiver member 102 can include a threaded inner surface410 that can engage with a set screw or other locking element receivedtherebetween to lock a spinal rod within the receiver member 102. Insome embodiments, the inner threaded portion 410 can have square threadse.g., to engage with counterpart external square threads of a set screw(see FIG. 14).

FIG. 5 is a front view of another embodiment of a bone anchor assembly500 of the present disclosure with reduction tabs 502 extendingproximally from the spaced apart arms 512, 514 of the receiver member504. The bone anchor assembly 500 of FIG. 5 can include any of thefeatures described herein.

Bone anchor assemblies 100, 500 of the present disclosure can include areceiver member 102, 504 having a taper in one or more directions. FIG.6 is a partially transparent view of the bone anchor assembly 100 ofFIG. 1 that shows, among other things, a taper 602 of the outer surfaceof the receiver member 102 in a first direction. More particularly, afirst pair of opposed sides 604, 606, shown in FIG. 6 as exterior wallsof the spaced-apart arms 112, 114, can have a first taper with respectto a first plane that contains a proximal-distal axis A1 of the receivermember 102 (i.e., the plane of the page of FIG. 6). Alternatively, FIG.60 shows an embodiment of a receiver member 5702 in which a first pairof opposed sides 6004, 6006, do not have a taper with respect to thefirst plane that contains a proximal-distal axis A1 of the receivermember. That is, the opposed sides 6004, 6006 of exterior walls of thespaced-apart arms 5712, 5714 have a substantially straight cylindricalshape.

FIG. 7 is a partially transparent side view of the bone anchor assembly100 of FIG. 1 in an orientation that is 90 degrees offset from theorientation shown in FIG. 6. FIG. 7 illustrates, among other things, ataper 702 of the outer surface of the receiver member 102 in a seconddirection. More particularly, a second pair of opposed sides 704, 706,shown in FIG. 7 as exterior walls of the receiver member 120 that are 90degrees offset from the first pair of opposed sides 604, 606, can have asecond taper with respect to a second plane (i.e., the plane of the pageof FIG. 7). The second plane contains the proximal-distal axis A1 of thereceiver member and is offset from the first plane described above. Thefirst plane and the second plane can be perpendicular to one another insome embodiments, though other offset angles are also possible.Accordingly, when implanted into a patient's spine, the receiver member102 can have walls that taper in both the cephalad-caudal direction andthe medial-lateral direction, for example. Taper of the receiver member102 with respect to two offset planes can aid in instrument attachmentto the receiver member 102 as the angled characteristic of the receivermember 102, i.e., the tapering of exterior walls 604, 606, 704, 706 oran outer surface of the receiver member 102 in two directions, can guidesurgical instruments to self-center during attachment to the receivermember. In some embodiments, such as the embodiment shown in FIGS.57-62, the receiver member may only taper in a single direction. Such aconfiguration can still provide self-centering guidance duringattachment of an instrument to the receiver member. FIGS. 8 and 9 arenon-transparent front and side views of the bone anchor assembly 100 ofFIG. 1 in the orientations shown in FIGS. 6 and 7, respectively. Theinwards taper 604, 606, 704, 706 of the receiver member 102 towards theproximal end of the receiver member 102 can likewise be seen in thesefigures. FIGS. 8 and 9 illustrate that, in some embodiments, thetapering in multiple planes can be achieved using different surfacegeometries. For example, in the front view of FIG. 8 the surfaces 604,606 can have a curved shape that creates a conical first taper. Thesurfaces 704, 706, however, can be planar surfaces angled toward oneanother to create a second taper. As noted above, in some embodimentsonly one of these tapers may be utilized. For example, in the embodimentshown in FIGS. 57-62, cylindrical surfaces 6004, 6006 do not taper whileplanar surfaces 7004, 7006 include a similar taper as surfaces 704, 706in FIGS. 7 and 9.

Returning to FIGS. 6 and 7, the bone anchor assembly 100 can include adrag ring 204 disposed within a recess or groove 1702 (see FIG. 17)formed in a distal portion 120 of the receiver member 102. The drag ring204 can create a friction fit between an interior surface 204′ of thedrag ring 204 and an exterior surface of the shank head 302, such thatthe receiver member 102 of the bone anchor assembly 100 canprovisionally maintain a position relative to the bone shank 104 priorto a full locking of the bone anchor assembly 100, e.g., with a setscrew or other locking element. In some embodiments, the drag ring 204can be disposed within the distal portion 120 of the receiver member 102prior to insertion of the shank head 302. Further details on drag ringscan be found in U.S. Pat. No. 7,087,057, the entire contents of whichare incorporated by reference herein. As noted above, the distal end 120of the receiver member 102 can include a polyaxial seat 608 forpolyaxially seating the head 302 of the bone shank 104. This polyaxialconnection can allow full range of motion of the bone shank 104 relativeto the receiver member 102. For example, a spherical recess in thedistal end 120 of the receiver member 102 (see polyaxial seat 1704 inFIG. 17) can receive a spherical portion of the shank head 302.

FIGS. 10-12 illustrate one embodiment of a compression cap 202 of thepresent disclosure. FIG. 10 is a perspective view of one embodiment of acompression cap 202, FIG. 11 is a front view of the compression cap 202of FIG. 10, and FIG. 12 is a cross-sectional view of the compression cap202 as shown in FIG. 11. As noted above, the outer surface of thecompression cap 202 can include depressions or recesses 304 that canreceive material from the receiver member 102 that is displaced during aswage that can form the second rocker feature 406. A proximal portion ofthe compression cap can form a seat for receiving a spinal rod. Moreparticularly, two planar surfaces 1002, 1004 of the compression cap canbe angularly offset from one another to form a substantially “V” shapedgroove that can seat a spinal rod of varying diameters. This is incomparison to conventional compression caps that often include a curvedproximal surface with a radius matching a single spinal rod diameter.

FIGS. 13A-13D illustrate various aspects of one embodiment of a boneshank 104 of the present disclosure. FIG. 13A shows the bone anchorassembly 100 of FIG. 1. FIG. 13B shows a top perspective view of thebone shank 104 in isolation. FIG. 13C shows an enlarged view of a distalend of the bone-engaging portion 108 of the bone shank 104. FIG. 13Dshows a partially transparent enlarged view of the distal end of thebone-engaging portion 108 of the bone shank 104. External threads 1302can extend along the bone-engaging portion 108 of the shank 104. Variousthread forms can be utilized for shanks of the present disclosure,including solid dual lead, solid cortical fix, cannulated dual lead,cannulated cortical fix, and cannulated cortical fix fenestratedthreads. The bone shank 104 can have a quick-start tip 1304, withthreads that extend distally to a distal tip 3410 of the bone engagingportion 1310. In this manner, the threads 1302 can extend to the contactsurface between the bone shank 104 and the bone (not shown), which canprovide immediate purchase of the thread into bone. In many conventionalscrews, a rounded tip is often used distal to the threads, which canrequire driving the screw into the bone axially some distance beforethreads can grip the bone.

A recess 1306 can be centered and formed in the distal tip 1310 of thebone shank 104. This recess 1306, which can be referred to as acentering recess, can be used to support the distal bone-engagingportion 108 of the shank 104 in a centered manner during themanufacturing process. In some embodiments, the centering recess can bea blind bore that extends proximally from the distal tip 1310 of thebone-engaging portion 108 (e.g., as shown in the partially transparentview of FIG. 13D). In other embodiments, the centering recess can be afull cannulated recess that extends from the proximal end to the distalend of the bone shank 104. Such a recess can allow, for example, forintroduction of the shank 104 over a guidewire, delivery of cement orother flowable material through the shank 104 into bone, etc. A drivefeature 1308 can be formed in the proximal head 302 of the bone shank104 to allow a driver to control rotation of the anchor duringimplantation, etc. Any of a variety of drive feature designs can beutilized, including square drive, hex drive, lobed drives, etc. Theillustrated embodiment includes a T27 drive feature.

FIG. 14 illustrates one embodiment of a set screw 1400 of the presentdisclosure. The set screw 1400 and proximal portion of the receivermember 102 inner surface 206 (see FIG. 2) can each have complementarysquare threads 1402 (or other thread forms) formed thereon. As notedabove, the set screw 1400 can have a drive feature 1404 formed therein,such as the above-noted T27 drive feature 1404. FIGS. 15A and 15Billustrate one embodiment of a reducer instrument 1500, in the form of areducer fork, engaging with a distal rocker feature 1502 of a boneanchor assembly 1501. The reducer instrument 1500 can couple with thereceiver member 1503 when the bone anchor assembly 1501 is implantedinto bone by engaging the distal rocker features 1502 on either side ofthe receiver member 1503, e.g., with counterpart projections formed onthe arms of the reducer instrument 1500. The reducer instrument 1500 canbe pivoted or rocked to move a spinal rod 1506 distally into the recessof the receiver member 1503. Further, the offset of the instrument 1500from the receiver member 1503 created by the fork arm shape and pivotingmotion can leave a proximal end of the receiver member 1503 unobstructedsuch that a set screw 1400 or other locking element can be insertedusing a driver 1504 to lock the spinal rod 1506 to the receiver member1503.

FIGS. 16-19 provide additional detail views of the bone anchor assembly100. For example, FIG. 16 shows a top or proximal end view of theassembly 100. This figure illustrates that the spaced apart arms 112,114 of the receiver member 102 generally lie along a circle 1602. Forexample, each of the unilateral attachment features 408 found at thelateral ends of the spaced apart arms 112, 114 can be positioned anequal distance from the centerline of the assembly, i.e., at a distanceequal to the radius of the circle 1602.

FIG. 17 shows a cross-sectional view bisecting the receiver member 102through the middle of the U-shaped recess 119 formed between the spacedapart arms 112, 114 at the proximal end 110 of the receiver member 102.The figure affords a better view of the interior of the receiver member102, including two of the unilateral attachment features 408 formed ateither lateral end of the receiver member arm 112, threads 410 formed ata proximal end of the interior surface of the arm 112 to receive a setscrew, an intermediate unthreaded portion 1701, a groove 1702 thatreceives the spring clip or drag ring 204, and a polyaxial seat 1704formed at a distal end 120 of the receiver member 104 that can seat thespherical head 302 of the shank 104.

FIG. 18 shows a detail view of an exterior proximal portion 110 of thereceiver member 102, including the notch or groove 402 formed in anouter sidewall of the spaced apart arms 112, 114 of the receiver member102, as well as the first rocker feature 404 that intersects the groove402. Like the groove 402, the first rocker feature 404 is recessed belowan outer surface 604 of the arm. Further, the first rocker feature 404extends proximally above the top or proximal surface of the groove 402,as shown by the arc 1802. The arc 1802 provides a greater surface areafor force transfer when coupled to a rocker fork reduction instrumentthat typically includes cylindrical pins that seat within the firstrocker feature recess 404. Without the arc 1802, the cylindrical pin ofthe rocker fork instrument would make a substantially point or linecontact with the substantially planar upper or proximal surface of thegroove 402.

FIG. 19 illustrates an exploded view of the bone anchor assembly 100. Asshown in the figure, in one embodiment the bone anchor 100 can beassembled by top loading or distally advancing the spring clip or ring204 relative to the receiver member 102 and allowing the springclip/ring 204 to expand into the groove 1702. The shank 104 can then betop loaded or advanced distally through the interior of the receivermember 102 such that the distal bone-engaging portion 108 of the shank104 extends out the through-hole 101 (shown in FIG. 17) formed in thebottom of the receiver member 102, the spherical head 302 of the shank104 rests in the polyaxial seat 1704 of the receiver member 102, and thedrag clip/ring 204 frictionally engages the spherical head 302. Thecompression cap 202 can also be top loaded or distally advanced into theinterior of the receiver member 102, and a swaging operation can beperformed to lock the compression cap 202 against removal from theinterior of the receiver member 102. Despite being locked againstcomplete removal after swaging, the compression cap 202 can stilltranslate through a range of motion relative to the receiver member 102and shank 104, such polyaxial movement of the receiver member 102relative to the shank 104 can be selectively controlled by varyingdistal force placed on the compression cap 202 that drives it intofrictional contact with the proximal end of the bone shank sphericalhead 302.

FIGS. 20-56 illustrate additional embodiments of bone anchor assembliesaccording to the present disclosure. These embodiments utilize many ofthe above-described features but can be configured for use with largerdiameter screw shanks. In addition, the receiver members shown in theseembodiments can be configured to bias shank angulation to one side or inone direction using a “favored angle” distal portion that allows agreater degree of shank angulation in one direction versus the oppositedirection.

The bone anchor assemblies of these embodiments can generally include areceiver member or head, a compression member or cap, a locking sphere,and a shank. The bone anchor assembly can be assembled by inserting theproximal portion of the screw shank up through a distal hole formed inthe receiver member. A locking sphere can be dropped into the proximalend of the receiver member and pressed onto the screw shank. The spherecan be locked onto the shank with a rib that fits into a recess insideof the locking sphere. A compression component can be loaded into thereceiver member from the proximal end and retained in place, e.g., byswaging, to hold the assembly together. In certain embodiments, a dragfeature can also be incorporated, such as by including a drag ring,spring clip, etc., disposed within the receiver member and around thelocking sphere to provide a drag force opposing polyaxial movement ofthe receiver member relative to the screw shank.

FIGS. 20-34 illustrate different views of one embodiment of a largediameter favored angle bone anchor assembly 2000 according to thepresent disclosure, and FIGS. 35-45 illustrate detail views ofcomponents of the assembly. More particularly, FIGS. 20 and 21 provideopposing perspective views of a bone anchor assembly 2000. FIG. 22provides an exploded view of the bone anchor assembly 2000. FIG. 23provides a cross-sectional view of the bone anchor assembly 2000. FIG.24 provides a partially transparent perspective view of the proximalportion of the bone anchor assembly 2000. FIG. 25 provides a front viewof the proximal portion of the bone anchor assembly 2000. FIG. 26provides a front cross-sectional view of the proximal portion of thebone anchor assembly 2000. FIGS. 27 and 28 provide opposing side viewsof the proximal portion of the bone anchor assembly 2000. FIGS. 29 and30 provide top and bottom views of the bone anchor assembly 2000. FIGS.31-34 illustrate various features of the receiver member 2002 of thebone anchor assembly 2000. FIGS. 35-38 provide perspective, front, top,and bottom views of the receiver member 2002. FIGS. 39 and 40 provideperspective and cross-sectional views of the locking sphere 2006 of thebone anchor assembly 2000. FIG. 41 provides a perspective view of a dragring 2010 of the bone anchor assembly 2000. Finally, FIGS. 42-45 provideperspective, front, and cross-sectional views of a compression member2008 of the bone anchor assembly 2000.

As shown in FIGS. 20-34, one embodiment of a large diameter favoredangle bone anchor assembly 2000 can include a receiver member 2002 and abone anchor or shank 2004 having a proximal head portion 2204 and adistal bone-engaging portion 2007. The receiver member 2002 can have aproximal end 2009 defined by a pair of spaced apart arms 2013, 2015forming a U-shaped recess 2019 (also referred to as a rod-receivingrecess or slot) therebetween to receive a spinal fixation element (notshown), such as a spinal rod. A polyaxial seat 2602 (see FIG. 26) can beformed in a distal end 2011 of the receiver member 2002 for polyaxiallyseating a locking sphere 2006 coupled to the proximal portion 2204 ofthe bone anchor/shank 2004. The bone anchor assembly 2000 can furtherinclude a compression member or cap 2008 and a drag ring 2010 disposedwithin the receiver member 2002, each of which can contact the lockingsphere 2006 to exert friction forces thereon that can selectively resistand/or prevent any relative movement of the receiver member 2002relative to the bone anchor/shank 2004.

The bone anchor assembly 2000 can be similar in many respects to thebone anchor assemblies described above, and can include any of thevarious features described above in any combination. For example, thereceiver member 2002 can include any of a variety of features tofacilitate engagement of a surgical instrument with the bone anchorassembly. These can include a groove or channel 2012 formed in an outersurface at the proximal end of each spaced apart arm 2013, 2015 of thereceiver member 2002 that can define a “top-notch” feature that can beengaged with a corresponding portion of an instrument, such as aprojection, to facilitate coupling of the instrument to the receivermember.

In other embodiments, the receiver member 2002 can include a proximalrocker feature (or first recess) 2014 formed in a proximal portion 2009of the receiver member 2002 that can be used to facilitate reducing arod distally into the U-shaped recess 2019 of the receiver member 2002.The proximal rocker reducer feature 2014 can allow a rocker instrumentto pivotably couple to the receiver member 2002 for reduction of aspinal fixation element into the receiver member 2002 using a leveringor rocking motion. The proximal rocker feature 2014 can be a bilateralcircular detail or recess that intersects the top-notch feature/groove2012, as described above. In other embodiments, however, differentshapes can be utilized for the proximal rocker feature recess.

In some embodiments, the receiver member 2002 can additionally oralternatively include a distal rocker feature (also referred to as asecond recess) 2016. The distal rocker feature 2016 can be formed in thereceiver member 2002 at a position distal to the proximal rocker feature2014. The second or distal rocker feature 2016 can provide analternative coupling position for a rocker instrument, such as a reducerrocker fork, to the proximal rocker feature 2014. The second rockerfeature can also be a swage feature used to retain a compression member2008 within the receiver member 2002. During assembly, for example, aswaging process can form the second rocker feature 2016 and displacereceiver member material into a recess 4202 (see FIG. 42) formed in thecompression member 2008 to constrain it within the receiver member 2002and prevent, e.g., its removal out the proximal end 2009 of the receivermember 2002. The second rocker feature 2016 can be formed on opposingsides of the receiver member and material in each arm 2013, 2015 of thereceiver member 2002 can be displaced by swaging into the recessesformed on opposing sides of the compression cap 2008.

The receiver member 2002 can include at least one unilateral attachmentfeature 2018 that can enable a surgical instrument to couple to orengage with the receiver member 2002 in a manner that leaves therod-receiving slot 2019 unobstructed, e.g., by allowing attachment of aninstrument to the receiver member 2002 by engaging only one arm 2013 or2015 of the receiver member 2002. In one embodiment, the receiver member2002 can include a unilateral attachment feature 2018 on four proximalquadrants of the receiver member 2002. For example, a unilateralattachment feature 2018 can be formed on opposing laterally-facing edgesof each of the spaced apart arms 2013, 2015. A surgical instrument canattach to two adjacent unilateral features 2018 on one side of thereceiver member 2002, leaving the rod-receiving slot 2019 open toreceive a spinal fixation rod and/or set screw introduced distally fromthe proximal end 2009 of the receiver member 2002, as explained above.

As described above, the receiver member 2002 can receive spinal fixationelements of multiple sizes. For example, spinal rods having a diameterof about 5.5 mm or a diameter of about 6.0 mm can be received within therod-receiving recess 2019. A proximal portion of the spaced apart arms2013, 2015 of the receiver member 2002 can include a threaded innersurface 2020 that can engage with a set screw or other locking elementreceived therebetween to lock a spinal rod within the receiver member2002. In some embodiments, the inner threaded portion 2020 can havesquare threads e.g., to engage with counterpart external square threadsof a set screw (e.g., see FIG. 14).

The receiver member 2002 can also include a taper in at least onedirection. FIG. 33 is a partially transparent view of the bone anchorassembly 2000 of FIG. 20 that shows, among other things, a taper 3302 ofthe outer surface of the receiver member 2002 in a first direction. Moreparticularly, a first pair of opposed sides 3304, 3306, shown in FIG. 33as exterior walls of the spaced-apart arms 2013, 2015, can have a firsttaper with respect to a first plane that contains a proximal-distal axisA1 of the receiver member (i.e., the plane of the page of FIG. 33). Asshown above in FIG. 7, a second taper can be included in an orientationthat is 90 degrees offset from the orientation shown in FIG. 33, i.e., asecond taper with respect to a second plane that contains theproximal-distal axis A1 of the receiver member and is offset from thefirst plane. This second taper is not required, however, and, as shownin FIGS. 20, 25, and 36, among others, the bone anchor assembly 2000does not include a second taper. Instead, the surfaces 2030, 2031adjacent planar tapered surfaces 3304, 3306, have a straight cylindricalprofile. In embodiments where multiple tapers are included, the firstplane and the second plane can be perpendicular to one another in someembodiments, though other offset angles are also possible. Accordingly,in some embodiments, when implanted into a patient's spine, the receivermember 2002 can have walls that taper in both the cephalad-caudaldirection and the medial-lateral direction, for example. Taper of thereceiver member 2002 with respect to one or two offset planes can aid ininstrument attachment to the receiver member as the angledcharacteristic of the receiver member, i.e., the tapering of exteriorwalls or an outer surface of the receiver member in one or twodirections, can guide surgical instruments to self-center duringattachment to the receiver member.

In addition to the above-described features of the receiver member 2002,the receiver member can be configured to provide a greater degree ofangulation in a first direction relative to a second direction that isopposite the first direction. For example, the receiver member 2002 caninclude a distal facing surface 2022 that is obliquely angled relativeto a central proximal-distal axis A1 of the receiver member. This caneffectively angle a hole 2202 (see FIG. 22) formed in the distal facingsurface of the receiver member 2002 to one side, thereby allowing agreater degree of angulation of the bone anchor 2004 toward that side incomparison to an opposite side. This can bias the bone anchor assembly2000 to favor angulation in one direction. FIG. 25 illustrates the angleα created between the central proximal-distal axis A1 and the plane ofthe distal facing surface 2022.

The bone anchor or shank 2004 can similarly include any of the variousfeatures described above. For example, the bone anchor 2004 can includeexternal threads 2024 extending along the bone-engaging portion 2007 ofthe shank 2004. Various thread forms can be utilized for shanks of thepresent disclosure, including solid dual lead, solid cortical fix,cannulated dual lead, cannulated cortical fix, and cannulated corticalfix fenestrated threads. The bone shank 2004 can have a quick-start tip3402, as shown in FIG. 34, with threads that extend distally to a distaltip 3410 of the bone engaging portion 2007. In this manner, the threads2024 can extend to the contact surface between the bone shank 2004 andthe bone, which can provide immediate purchase of the thread 2024 intobone.

In addition, a recess 3404, also shown in FIG. 34, can be centered andformed in the distal tip of the bone shank 2004. This recess 3404, whichcan be referred to as a centering recess, can be used to support thedistal bone-engaging portion 2007 of the shank 2004 in a centered mannerduring the manufacturing process. In some embodiments, the centeringrecess 3404 can be a blind bore that extends proximally from the distaltip of the bone-engaging portion (e.g., as shown in the partiallytransparent view of FIG. 34). In other embodiments, the centering recess3404 can be a full cannulated recess that extends from the proximal endto the distal end of the bone shank 2004. Such a recess can allow, forexample, for introduction of the shank 2004 over a guidewire, deliveryof cement or other flowable material through the shank 2004 into bone,etc. A drive feature 2302 (see FIGS. 23 and 29) can be formed in theproximal head 2204 of the bone shank 2004 to allow a driver to controlrotation of the anchor during implantation, etc. Any of a variety ofdrive feature designs can be utilized, including square drive, hexdrive, lobed drives, etc. The illustrated embodiment includes a T27drive feature.

The bone anchor assembly 2000 can be configured for use with largerdiameter bone anchors or shanks 2004. For example, in some embodimentsthe bone anchor assembly 100 described above can have a bone anchor 104with a shank diameter of up to about 7 mm. Above about that size, thebone anchor can become too large for bottom loading through the holeformed in the distal surface of the receiver member, especially when thebone anchor includes a spherically-shaped proximal end. The bone anchorassembly 2000 can provide for larger size bone anchors by utilizing abone anchor with a relatively uniform diameter or column-shaped proximalend that can be bottom loaded into the receiver member 2002 through thehole 2202 and coupled to a locking sphere 2006 that is top loaded intothe receiver member. This modular configuration can allow, in someembodiments, the use of bone anchors with a diameter between about 7 mmand about 12 mm, though this configuration could also be used for anysmaller diameter in place of a single-component bone anchor like thatshown in the embodiment of FIG. 1.

As shown in FIG. 22, the bone anchor 2004 can include a proximal portion2204 configured to couple with the locking sphere 2006. The proximalportion 2204 can include a rib, protrusion, or other feature 2206 formedon an outer surface thereof that can interface with a recess or othercomplementary feature 4002 (see FIG. 40) formed on an inner surface ofthe locking sphere 2006. This arrangement can secure the locking sphere2006 relative to the bone anchor 2004 such that the bone anchor 2004 canmove polyaxially relative to the receiver member 2002 when the lockingsphere 2006 is disposed in the polyaxial seat 2019 of the receivermember 2002. Further, movement of the bone anchor 2004 relative to thereceiver member 2002 can be controlled using friction forces exerted onthe locking sphere 2006, as explained in more detail below.

As shown in FIGS. 39 and 40, the locking sphere 2006 can have aspherical outer surface and a columnar inner surface configured toreceive the proximal end portion 2204 of the bone anchor 2004. Thelocking sphere 2006 can also include one or more relief slits 3902formed therein to allow for deformation of the locking sphere 2006 whencoupling with the bone anchor 2004. In the illustrated embodiment, twodifferent shapes of relief slits 3902, 3904 are provided in analternating pattern around the circumference of the locking sphere 2006.The inner surface of the locking sphere 2006 can include the recess 4002that can receive the rib 2206 formed on the outer surface of theproximal portion 2204 of the bone anchor 2004 to help secure the twocomponents relative to one another when coupled.

As shown in FIGS. 22-24, 26, and 41, the bone anchor assembly 2000 caninclude a drag ring 2010 disposed within a recess or groove 2208 (seeFIGS. 22, 26, and 35) formed in a distal portion 2011 of the receivermember 2002. The drag ring 2010 can create a friction fit between aninterior surface of the drag ring 2010 and an exterior surface of thelocking sphere 2006, such that the receiver member 2002 of the boneanchor assembly can provisionally maintain a position relative to thebone shank 2004 prior to a full locking of the bone anchor assembly,e.g., with a set screw or other locking element. The drag ring 2010 canbe positioned above an equator or widest diameter of the locking sphere2006. This can mean, in some embodiments, that the drag ring 2010 can bedisposed within the distal portion 2011 of the receiver member 2002after the locking sphere 2006 is top loaded into the distal portion ofthe receiver member.

FIGS. 42-45 illustrate one embodiment of a compression member or cap2008 of the present disclosure. FIGS. 42 and 43 are perspective views ofone embodiment of a compression member 2008, FIG. 44 is a front view ofthe compression member 2008, and FIG. 45 is a cross-sectional view ofthe compression member 2008. As noted above, the outer surface of thecompression cap 2008 can include depressions or recesses 4202 that canreceive material from the receiver member 2002 that is displaced duringa swage that can form the second rocker feature. A proximal portion ofthe compression member 2008 can form a seat 4210 for receiving a spinalrod. More particularly, two planar surfaces 4204, 4206 of thecompression member can be angularly offset from one another to form asubstantially “V” shaped groove that can seat a spinal rod of varyingdiameters. A bottom surface 4208 of the compression member 2008 caninclude a substantially spherical surface configured to contact thelocking sphere 2006 and exert a friction force thereon when thecompression member 2008 is advanced distally relative to the receivermember 2002 (e.g., by a user tightening a set screw into the threadsformed in the proximal portion of the receiver member).

FIGS. 46-49 illustrate different views of another embodiment of a largediameter favored angle bone anchor assembly 4600 according to thepresent disclosure. More particularly, FIGS. 46 and 47 provide opposingperspective views of a bone anchor assembly 4600. FIG. 48 provides anexploded view of the bone anchor assembly 4600. FIG. 49 provides across-sectional view of the bone anchor assembly 4600.

In the embodiment of FIGS. 46-49, the receiver head 2002, locking sphere2006, compression member 2008, and drag ring 2010 can be the same asthose described above in connection with the embodiment of FIG. 20, buta differently-configured bone anchor or shank 4602 can be provided. Thebone anchor 4602 can include a plurality of threaded sections that canbe configured to increase fixation of the bone anchor assembly 4600 inbone. For example, the bone anchor 4602 can include a first distalthreaded section 4604 that has a first pitch and a first number ofthread starts and a second proximal threaded section 4606 that has asecond pitch less than the first pitch and a second number of threadstarts greater than the first number of thread starts. The differentthreaded sections or portions 4604, 4606 can have a constant lead (equalto thread starts multiplied by thread pitch), i.e., can translate thebone anchor 4602 an equal distance in a direction parallel to alongitudinal axis of the bone anchor shaft when rotated one turn (360°).

For a bone anchor assembly designed to be implanted through the pedicleof a vertebra, for example, the threaded distal section 4604 can beconfigured to engage cancellous bone in the anterior vertebral body ofthe vertebra and the threaded proximal section 4606 can be configured toengage cortical bone of the pedicle of the vertebra. Use of threadedsections with a constant lead can facilitate insertion of the anchor4602 into the vertebra and prevent stripping of the pedicle wall.Additional details regarding the bone anchor 4602 and its plurality ofthreaded sections can be found in U.S. Pat. No. 9,155,580, entitled“Multi-threaded Cannulated Bone Anchors,” the entire contents of whichare incorporated by reference herein.

FIGS. 50-54 illustrate different views of yet another embodiment of alarge diameter favored angle bone anchor assembly 5000 according to thepresent disclosure. More particularly, FIGS. 50 and 51 provide opposingperspective views of a bone anchor assembly 5000. FIG. 52 provides anexploded view of the bone anchor assembly 5000. FIG. 53 provides across-sectional view of the bone anchor assembly 4600. FIG. 54 providesa front view of the bone anchor assembly 5000 in an angulated state.

In the embodiment of FIGS. 50-54, the receiver head 2002, locking sphere2006, compression member 2008, and drag ring 2010 can be the same asthose described above in connection with the embodiments of FIGS. 20 and46, but a differently-configured bone anchor or shank 5002 can beprovided. The bone anchor 5002 can include a first, distal threadedportion or section 5004 and a second portion or section 5006 withoutthreads that is disposed between the first portion 5004 and the proximalportion 5007 of the bone anchor 5002. The second portion 5006 can have asmooth outer surface with a diameter that is less than a maximum majordiameter of the threaded portion 5004, i.e., less than the majordiameter near the proximal end 5009 of the first portion 5004 before thediameter begins to taper closer to a distal end 5011 of the bone anchor5002. In some embodiments, the diameter of the second portion 5006 canbe close to the maximum major diameter of the threaded portion 5004 tomaximize the strength of the bone anchor 5002. In some embodiments, thediameter of the second portion 5006 can be between a maximum minordiameter and a maximum major diameter of the threaded portion 5004.

The second portion 5006 can have a variety of lengths according to adesired overall length of the bone anchor 5002. In some embodiments, thelength of the second portion 5006 can be at least about 30% of a lengthof the first portion 5004, and in some embodiments the length of thesecond portion can be between about 30% and about 90% of the length ofthe first portion 5004.

The bone anchor 5002 can be useful in certain applications where alonger screw with maximum strength is desirable. One such application isin “SAI” trajectories, i.e., procedures where the bone anchor isintroduced through the sacral alar such that its distal end arrives inthe ilium. In such procedures, it can be desirable to provide theextended second portion 5006 without threads and with a maximum strengthto resist forces exerted thereon. Accordingly, the unthreaded secondportion 5006 can be provided that has a diameter just under that of themaximum major diameter of the threaded first portion 5004.

FIG. 54 illustrates the bone anchor assembly 5000 in an angulated state,where a proximal-distal axis A1 of the receiver member 2002 is obliquelyangled relative to a proximal-distal axis A2 of the bone anchor 5002.This is in contrast to the positioning shown in FIGS. 50-53 where theaxes A1 and A2 are aligned and coaxial with one another. As noted above,the “favored angle” configuration of the receiver member 2002 can allowa greater degree of angulation in one direction versus a second oppositedirection. For example, a greater degree of angulation in the directionshown in FIG. 54, where a distal portion of axis A2 is disposed to theleft of axis A1 in the plane of the figure, is possible in comparison toan opposite direction of angulation, where a distal portion of axis A2would be disposed to the right of the axis A1 in the plane of thefigure.

FIG. 55 illustrates still another embodiment of a large diameter favoredangle bone anchor assembly 5500 according to the present disclosure. Inthis embodiment, the receiver member 2002, locking sphere 2006,compression member 2008, and drag ring 2010 can be the same as thosedescribed above in connection with the embodiments of FIGS. 20, 46, and50, but a differently-configured bone anchor or shank 5502 can beprovided. In particular, the bone anchor assembly 5500 can include afenestrated bone anchor 5502. That is, the bone anchor 5502 can includea cannula or passage extending along its longitudinal axis from aproximal end toward a distal end thereof. In addition, the bone anchor5502 can include one or more outlets 5504 formed along a length thereofthat can intersect with the cannula or passage formed in the boneanchor. The one or more outlets 5504 can allow a flowable substance,e.g., a bone cement or other substance, to be introduced into the areasurrounding the bone anchor by injecting it into the cannula or passageat the proximal end of the bone anchor. The one or more outlets 5504 canbe disposed along any portion of the bone anchor 5502. In theillustrated embodiment, the outlets 5504 are shown disposed along adistal portion of the bone anchor 5502 with opposed outlets forming athrough-bore in the bone anchor that intersects the central cannula orpassage formed in the bone anchor. In some embodiments, thelaterally-facing outlets 5504 can be omitted such that the bone anchor5502 includes a single cannula extending from openings formed at itsproximal end 5508 and its distal end 5506.

The thread form of the bone anchor 5502 is similar to the embodimentshown in FIG. 46, though the illustrated fenestration of a bone anchorcan also be incorporated into any of the various bone anchorconfigurations disclosed herein. For example, it is within the scope ofthe present disclosure to provide a fenestrated screw shank having theform shown in the embodiment of any of FIG. 20 or FIG. 50 as well. Thismeans the present disclosure encompasses any combination of solid,cannulated, and/or fenestrated bone anchors having so-called “dual lead”threads (as shown in the embodiment of FIG. 20), “cortical fix” threads(as shown in the embodiment of FIG. 46), and/or “partial” threads (asshown in the embodiment of FIG. 50).

FIG. 56 illustrates another embodiment of a large diameter favored anglebone anchor assembly 5600 according to the present disclosure. In thisembodiment, the locking sphere 2006, compression member 2008, drag ring2010, and bone anchor 2004 are the same as those described above inconnection with the embodiment of FIG. 20, but a differently-configuredreceiver head 5602 is provided. In particular, the receiver member 5602can include one or more extended tabs 5604 protruding from a proximalend of the receiver head to facilitate manipulation of the receiver headand introduction of components, such as a set screw or other instrumentor component to help reduce and secure a rod in position relative to thereceiver member 5602. The one or more tabs 5604 can be integrally formedwith the receiver member 5602 or otherwise coupled thereto. In someembodiments, the one or more tabs can be configured to separate from thereceiver member 5602 when desired, e.g., at the end of an implantationprocedure after a rod is secured relative to the receiver member. Thiscan be accomplished in some embodiments by a user breaking the tabs at apredetermined position or otherwise separating them from the remainderof the receiver member 5602.

As with the fenestration feature described above, utilization ofextended tabs can be included with any of the various embodimentsdescribed herein. For example, one or more extended tabs can be includedin the receiver members of the embodiments of any of FIGS. 46 and 50 aswell.

FIGS. 57-66 illustrate additional embodiments of bone anchor assembliesaccording to the present disclosure. These embodiments utilize many ofthe above-described features. Similar to the embodiments explainedabove, the bone anchor assemblies of these embodiments can generallyinclude a receiver member or head, a compression member or cap, and ashank. In certain embodiments, a drag feature can also be incorporated,such as by including a drag ring, spring clip, etc., disposed within thereceiver member and around sphere proximal head of the shank to providea drag force opposing polyaxial movement of the receiver member relativeto the screw shank.

FIGS. 57-62 illustrate different views of one embodiment of a boneanchor assembly 5700 according to the present disclosure, and FIGS.63-66 illustrate detail views of a compression cap of the assembly. Moreparticularly, FIGS. 57 and 58 provide opposing perspective views of abone anchor assembly 5700. FIGS. 59A, 59B, and 60 provide detail viewsof a proximal portion of the assembly, FIG. 61 provides an exploded viewof the bone anchor assembly 5700, and FIG. 62 provides a cross-sectionalview of the bone anchor assembly 5700.

Turning to FIG. 57, the receiver member 5702 of bone anchor assembly5700 can include a proximal end 5703 defined by a pair of spaced apartarms 5712, 5714 forming a U-shaped recess 5719 (also referred to as arod-receiving recess or slot) therebetween to receive a spinal fixationelement (not shown), such as a spinal rod. A polyaxial seat 6202 can beformed in a distal end 5711 of the receiver member 5702 for polyaxiallyseating a proximal portion 5706 of the bone anchor/shank 5704. The boneanchor assembly 5700 can further include a compression member or cap5708 and a drag ring 5710 disposed within the receiver member 5702, eachof which can contact the proximal portion 5706 to exert friction forcesthereon that can selectively resist and/or prevent any relative movementof the receiver member 5702 relative to the bone anchor 5704.

Similar to the receiver member 102, the receiver member 5702 can includeat least one unilateral attachment feature 5718 that can enable asurgical instrument to couple to or engage with the receiver member 5702in a manner that leaves the rod-receiving slot 5719 unobstructed, e.g.,by allowing attachment of an instrument to the receiver member 5702 byengaging only one arm 5712 or 5714 of the receiver member 5702. In oneembodiment, the receiver member 5702 can include a unilateral attachmentfeature 5718 on four proximal quadrants of the receiver member 5702.Similar to unilateral attachment feature 408, a unilateral attachmentfeature 5718 can be formed on opposing laterally-facing edges of each ofthe spaced apart arms 5712, 5714. A surgical instrument can attach totwo adjacent unilateral features 5718 on one side of the receiver member5702, leaving the rod-receiving slot 5719 open to receive a spinalfixation rod and/or set screw introduced distally from the proximal end5703 of the receiver member 5702, as explained above.

As also shown in FIGS. 59A and 59B, each unilateral attachment feature5718 can have a distal planar surface 5711 having approximately a 90degree angle with a planar sidewall surface 5713, with a small radiusconcave surface 5902 connecting the two planar surfaces. The unilateralattachment feature 5718 can also include a medial planar surface 5904disposed at approximately a 90 degree angle with the planar surfaces5711 and 5713. Such a configuration can provide improved bracing optionsfor an instrument coupling to the receiver member 5702 using theunilateral attachment feature 5718. This can allow an instrument tosecurely couple to the receiver member 5702, even using only arelatively small area for purchase.

FIGS. 59A and 59B also illustrate further features of the rod slot 5719.In particular, a horizontal planar center or bottom surface 5905 of theU-shaped cut-out that separates the arms 5712, 5714 of the receivermember 5702 is connected to a planar vertical surface 5908 of each armby a curved surface 5906. Inclusion of the planar center surface 5905can allow use of a smaller radius curved surface 5906, which can ensurethat the curved surfaces 5906 do not interfere with a spinal rod as itpresses on the compression cap 5708, even when the rod is a maximum sizethat can be accommodated, e.g., it takes up the entire width of the slot5719 between the vertical surfaces 5908.

FIG. 59B illustrates an outline of a spinal fixation rod in a firstposition 5910 a as it is reduced distally into the rod slot 5719 of thereceiver member 5702. In the first position, the rod can contact theplanar upper surfaces 6104, 6106 of the compression cap 5708. At amaximum size, it can also touch the vertical surfaces 5908 of each arm5712, 5714. As the rod is further reduced, e.g., using an instrumentlike the rocker reducer instrument or set screw described above, it canmove to a second position 5910 b, as shown by arrow 5911. In doing so,it can urge the compression cap 5708 distally, thereby exerting alocking force onto the shank 5704. At the second position 5910 b, therod can reach a maximum distal position where it contacts the centerplanar surface 5905. As shown, the inclusion of the center planarsurface 5905 allows the use of smaller radius curved surfaces 5906 totransition to the vertical surfaces 5908, which can ensure there isclearance 5912 between the curved surfaces 5906 and the rod even at thesecond position 5910 b of maximum distal advancement relative to thereceiver member 5702. If a larger radius were used, e.g., a singlecurved bottom surface connecting the vertical surfaces 5908, it ispossible that the rod would impact the curved surface at lateralpositions before reaching a desired position of maximum distaladvancement, thereby reducing the locking force exerted on thecompression cap 5708.

As noted above, FIG. 60 illustrates that the receiver member 5702includes a first set of opposed sides, 6004, 6006, having asubstantially straight cylindrical profile without any taper in diameteralong a longitudinal axis of the receiver member 5702. A second set ofopposed sides offset from the first sides 6004, 6006, can be planar andinclude a taper such that a distance between the second set of opposedsides decreases moving proximally along the longitudinal axis of thereceiver member 5702. The first of the opposed sides 7004 (opposed side7006 is hidden from view opposite side 7004) can be seen in FIGS. 59Aand 59B, and their configuration is similar to that shown in FIG. 7.

FIGS. 63-66 illustrate a compression member or cap 5708 of the assembly5700. FIGS. 63 and 64 are perspective views of one embodiment of acompression member 5708, FIG. 65 is a front view of the compressionmember 5708, and FIG. 66 is a front cross-sectional view of thecompression member 5708. Similar to the compression cap 202, the outersurface of the compression cap 5708 can receive material from thereceiver member 5702 that is displaced during a swage that can form thesecond rocker feature 5722. The configuration of the compression cap5708 is different from the compression cap 202, however, in that itincludes opposed flat surfaces 6102 rather than recesses 304. Theopposed flat surfaces 6102 can simplify manufacturing and allow a largersurface area for contact. The opposed flat surfaces 6102 can be recessedrelative to a maximum outer diameter of the compression cap 5708 and aprotruding lip 6103 can be formed distal to the opposed flat surfaces.Accordingly, displaced material from the receiver member 5702 that ismoved inward during a swage operation can abut the opposed flat surfaces6102 and prevent the compression cap 5708 from being removed proximallyout of the receiver member by interfering with the lip 6103. Distaladvancement of the compression cap 5708 remains possible during, e.g.,locking where a set screw is tightened onto a rod disposed in the slot5719. The configuration of the opposed flat surfaces 6102 and thereceiver member 5702 can be seen in the cross-sectional view of FIG. 62.

A proximal portion of the compression cap 5708, similar to cap 202, canform a seat for receiving a spinal rod. More particularly, two planarsurfaces 6104, 6106 of the compression cap 5708 can be angularly offsetfrom one another to form a substantially “V” shaped groove. Thesubstantially flat planar surfaces 6104, 6106 can provide a seat toaccommodate spinal rods of varying diameters. A bottom surface 6108 ofthe compression member 5708 can include a substantially sphericalsurface configured to contact the locking sphere 5706 and exert afriction force thereon when the compression member 5708 is advanceddistally relative to the receiver member 5702 (e.g., by a usertightening a set screw into the threads formed in the proximal portionof the receiver member).

Various devices and methods disclosed herein can be used inminimally-invasive surgery and/or open surgery. While various devicesand methods disclosed herein are generally described in the context ofsurgery on a human patient, the methods and devices disclosed herein canbe used in any of a variety of surgical procedures with any human oranimal subject, or in non-surgical procedures.

Various devices disclosed herein can be constructed from any of avariety of known materials. Example materials include those which aresuitable for use in surgical applications, including metals such asstainless steel, titanium, nickel, cobalt-chromium, or alloys andcombinations thereof, polymers such as PEEK, ceramics, carbon fiber, andso forth. Further, various methods of manufacturing can be utilized,including 3D printing or other additive manufacturing techniques, aswell as more conventional manufacturing techniques, including molding,stamping, casting, machining, etc.

Various devices or components disclosed herein can be designed to bedisposed of after a single use, or they can be designed to be usedmultiple times. In either case, however, various devices or componentscan be reconditioned for reuse after at least one use. Reconditioningcan include any combination of the steps of disassembly, followed bycleaning or replacement of particular pieces, and subsequent reassembly.In particular, a device or component can be disassembled, and any numberof the particular pieces or parts thereof can be selectively replaced orremoved in any combination. Upon cleaning and/or replacement ofparticular parts, the device or component can be reassembled forsubsequent use either at a reconditioning facility, or by a surgicalteam immediately prior to a surgical procedure. Reconditioning of adevice or component can utilize a variety of techniques for disassembly,cleaning/replacement, and reassembly. Use of such techniques, and theresulting reconditioned device or component, are within the scope of thepresent disclosure.

Various devices or components described herein can be processed beforeuse in a surgical procedure. For example, a new or used device orcomponent can be obtained and, if necessary, cleaned. The device orcomponent can be sterilized. In one sterilization technique, the deviceor component can be placed in a closed and sealed container, such as aplastic or TYVEK bag. The container and its contents can be placed in afield of radiation that can penetrate the container, such as gammaradiation, x-rays, or high-energy electrons. The radiation can killbacteria on the device or component and in the container. The sterilizeddevice or component can be stored in the sterile container. The sealedcontainer can keep the device or component sterile until it is opened inthe medical facility. Other forms of sterilization are also possible,including beta or other forms of radiation, ethylene oxide, steam, or aliquid bath (e.g., cold soak). Certain forms of sterilization may bebetter suited to use with different devices or components, or portionsthereof, due to the materials utilized, the presence of electricalcomponents, etc.

In this disclosure, phrases such as “at least one of” or “one or moreof” may occur followed by a conjunctive list of elements or features.The term “and/or” may also occur in a list of two or more elements orfeatures. Unless otherwise implicitly or explicitly contradicted by thecontext in which it is used, such a phrase is intended to mean any ofthe listed elements or features individually or any of the recitedelements or features in combination with any of the other recitedelements or features. For example, the phrases “at least one of A andB,” “one or more of A and B,” and “A and/or B” are each intended to mean“A alone, B alone, or A and B together.” A similar interpretation isalso intended for lists including three or more items. For example, thephrases “at least one of A, B, and C,” “one or more of A, B, and C,” and“A, B, and/or C” are each intended to mean “A alone, B alone, C alone, Aand B together, A and C together, B and C together, or A and B and Ctogether.” In addition, use of the term “based on,” is intended to mean,“based at least in part on,” such that an un-recited feature or elementis also permissible.

Further features and advantages based on the above-described embodimentsare possible and within the scope of the present disclosure.Accordingly, the disclosure is not to be limited by what has beenparticularly shown and described. All publications and references citedherein are expressly incorporated herein by reference in their entirety,except for any definitions, subject matter disclaimers or disavowals,and except to the extent that the incorporated material is inconsistentwith the express disclosure herein, in which case the language in thisdisclosure controls.

Examples of the above-described embodiments can include the following:

-   -   1. A bone anchor assembly, comprising:        -   a bone anchor having a proximal head portion and a distal            threaded bone-engaging portion; and        -   a receiver member having a proximal end defined by a pair of            spaced apart arms forming a U-shaped recess therebetween, a            distal end having a polyaxial seat formed therein for            polyaxially seating the head portion of the bone anchor, a            groove formed in an outer surface of each of the spaced            apart arms at a proximal end thereof, a first recess formed            in the outer surface of each arm with at least a portion of            the first recess intersecting the groove, and a second            recess formed in an outer surface of the receiver member at            a position distal to the first recesses;        -   wherein the first recesses and the second recesses are            configured to couple to a surgical instrument.    -   2. The assembly of claim 1, wherein at least a portion of the        first recess in each arm extends proximally beyond the groove.    -   3. The assembly of claim 1 or 2, wherein each of the second        recesses is longitudinally aligned with one of the first        recesses.    -   4. The assembly of any of claims 1 to 3, wherein the first        recesses are configured to pivotably couple to a surgical        instrument.    -   5. The assembly of any of claims 1 to 4, wherein the pair of        second recesses are configured to pivotably couple to a surgical        instrument.    -   6. The assembly of any of claims 1 to 5, wherein the U-shaped        recess is configured to receive a spinal fixation element of        various sizes.    -   7. The assembly of any of claims 1 to 6, wherein each spaced        apart arm has a laterally-facing recessed portion formed on        opposite lateral edges of the arm, each of the lateral-facing        recessed portions facing away from a central proximal-distal        axis of the receiver member, wherein the lateral-facing recessed        portions are configured to engage with a surgical instrument        such that the U-shaped recess remains unobstructed.    -   8. The assembly of claim 7, wherein each of the lateral-facing        recessed portions extend distally from the proximal end of the        spaced apart arms.    -   9. The assembly of claim 7, wherein each lateral-facing recessed        portion has a concave distal surface.    -   10. The assembly of claim 7, wherein each lateral-facing        recessed portion has a first planar surface, a second planar        surface substantially perpendicular to the first planar surface,        and a curved surface therebetween.    -   11. The assembly of any of claims 1 to 10, wherein the proximal        ends of the spaced apart arms lie along a common circular        circumferential path.    -   12. The assembly of any of claims 1 to 11, wherein opposing        laterally-facing sides of the receiver member taper inward        towards the proximal end of the receiver member.    -   13. The assembly of any of claims 1 to 11, wherein a first pair        of opposed sides of the receiver member has a first taper with        respect to a first plane that contains a proximal-distal axis of        the receiver member.    -   14. The assembly of claim 13, wherein a second pair of opposed        sides of the receiver member has a second taper with respect to        a second plane that contains the proximal-distal axis and is        offset from the first plane.    -   15. The assembly of claim 14, wherein the first plane is        perpendicular to the second plane.    -   16. The assembly of any of claims 1 to 15, further comprising a        drag ring disposed within the receiver member, the drag ring        configured to exert a friction force on the head portion of the        bone anchor.    -   17. The assembly of any of claims 1 to 16, further comprising a        compression member disposed within the receiver member, wherein        a proximal portion of the compression member includes opposing        planar surfaces that are angularly offset from one another        forming a seat for receiving a spinal fixation element.    -   18. The assembly of claim 17, wherein material displaced in the        formation of the second recesses is configured to restrict        movement of the compression member relative to the receiver        member.    -   19. The assembly of claim 18, wherein the displaced material is        received within corresponding recesses formed in the compression        member.    -   20. The assembly of any of claims 1 to 19, further comprising a        pair of reduction tabs extending proximally from the pair of        spaced apart arms.    -   21. The assembly of any of claims 1 to 20, further comprising a        fixation element with external square threads configured to be        received between the spaced apart arms of the receiver member.    -   22. The assembly of any of claims [0207] to 21, wherein the bone        anchor includes a bore extending proximally from a distal tip of        the bone engaging portion.    -   23. The assembly of claim 22, wherein the bore extends through        an entire length of the bone anchor.    -   24. The assembly of claim 22, wherein the bore is a blind bore.    -   25. The assembly of any of claims 1 to 2423, wherein the distal        bone-engaging portion further comprises external threads that        extend distally along the bone-engaging portion to a distal tip        thereof.    -   26. A bone anchor assembly, comprising:        -   a bone anchor having a proximal head portion and a distal            threaded bone-engaging portion;        -   a receiver member having a proximal end defined by a pair of            spaced apart arms forming a U-shaped recess configured to            receive a spinal fixation element therebetween and a distal            end having a polyaxial seat formed therein for polyaxially            seating the head portion of the bone anchor;        -   wherein opposing laterally-facing sides of the receiver            member taper inward towards the proximal end of the receiver            member.    -   27. The assembly of claim 26, wherein a first pair of the        opposing laterally-facing sides of the receiver member has a        first taper with respect to a first plane that contains a        proximal-distal axis of the receiver member.    -   28. The assembly of claim 27, wherein a second pair of the        opposing laterally-facing sides of the receiver member has a        second taper with respect to a second plane that contains the        proximal-distal axis and is offset from the first plane.    -   29. The assembly of claim 28, wherein the first plane is        perpendicular to the second plane.    -   30. The assembly of any of claims 26 to 29, wherein the receiver        member further comprises a groove formed in an outer surface of        each of the spaced apart arms at a proximal end thereof, a first        recess formed in the outer surface of each arm with at least a        portion of the first recess intersecting the groove, and a        second recess formed in an outer surface of the receiver member        at a position distal to the first recesses;        -   wherein the first recesses and the second recesses are            configured to couple to a surgical instrument.    -   31. The assembly of claim 30, wherein at least a portion of the        first recess in each arm extends proximally beyond the groove.    -   32. The assembly of claim 30 or 31, wherein each of the second        recesses is longitudinally aligned with one of the first        recesses.    -   33. The assembly of any of claims 30 to 32, wherein the first        recesses are configured to pivotably couple to a surgical        instrument.    -   34. The assembly of any of claims 30 to 33, wherein the pair of        second recesses are configured to pivotably couple to a surgical        instrument.    -   35. The assembly of any of claims 26 to 34, wherein the U-shaped        recess is configured to receive a spinal fixation element of        various sizes.    -   36. The assembly of any of claims 26 to 35, wherein each spaced        apart arm has a laterally-facing recessed portion formed on        opposite lateral edges of the arm, each of the lateral-facing        recessed portions facing away from a central proximal-distal        axis of the receiver member, wherein the lateral-facing recessed        portions are configured to engage with a surgical instrument        such that the U-shaped recess remains unobstructed.    -   37. The assembly of claim 36, wherein each of the lateral-facing        recessed portions extend distally from the proximal end of the        spaced apart arms.    -   38. The assembly of claim 36, wherein each lateral-facing        recessed portion has a concave distal surface.    -   39. The assembly of claim 38, wherein each lateral-facing        recessed portion has a first planar surface, a second planar        surface substantially perpendicular to the first planar surface,        and a curved surface therebetween.    -   40. The assembly of any of claims 26 to 39, wherein the proximal        ends of the spaced apart arms lie along a common circular        circumferential path.    -   41. The assembly of any of claims 26 to 40, further comprising a        drag ring disposed within the receiver member, the drag ring        configured to exert a friction force on the head portion of the        bone anchor.    -   42. The assembly of any of claims 26 to 41, further comprising a        compression member disposed within the receiver member, wherein        a proximal portion of the compression member includes opposing        planar surfaces that are angularly offset from one another        forming a seat for receiving a spinal fixation element.    -   43. The assembly of claim 42, wherein material displaced in the        formation of the second recesses is configured to restrict        movement of the compression member relative to the receiver        member.    -   44. The assembly of claim 43, wherein the displaced material is        received within corresponding recesses formed in the compression        member.    -   45. The assembly of any of claims 26 to 44, further comprising a        pair of reduction tabs extending proximally from the pair of        spaced apart arms.    -   46. The assembly of any of claims 30 to 45, further comprising a        fixation element with external square threads configured to be        received between the spaced apart arms of the receiver member.    -   47. The assembly of any of claims 30 to 46, wherein the bone        anchor includes a bore extending proximally from a distal tip of        the bone engaging portion.    -   48. The assembly of claim 47, wherein the bore extends through        an entire length of the bone anchor.    -   49. The assembly of claim 47, wherein the bore is a blind bore.    -   50. The assembly of any of claims 30 to 49, wherein the distal        bone-engaging portion further comprises external threads that        extend distally along the bone-engaging portion to a distal tip        thereof.    -   51. A bone anchor assembly, comprising:        -   a bone anchor having a proximal head portion and a distal            threaded bone-engaging portion;        -   a receiver member having a proximal end defined by a pair of            spaced apart arms forming a U-shaped recess configured to            receive a spinal fixation element therebetween and a distal            end having a polyaxial seat formed therein for polyaxially            seating the head portion of the bone anchor;        -   wherein proximal ends of the spaced apart arms lie along a            common circular circumferential path.    -   52. The assembly of claim 51, wherein the receiver member        further comprises a groove formed in an outer surface of each of        the spaced apart arms at a proximal end thereof, a first recess        formed in the outer surface of each arm with at least a portion        of the first recess intersecting the groove, and a second recess        formed in an outer surface of the receiver member at a position        distal to the first recesses;        -   wherein the first recesses and the second recesses are            configured to couple to a surgical instrument.    -   53. The assembly of claim 52, wherein at least a portion of the        first recess in each arm extends proximally beyond the groove.    -   54. The assembly of claim 52 or 53, wherein each of the second        recesses is longitudinally aligned with one of the first        recesses.    -   55. The assembly of any of claims 51 to 54, wherein the first        recesses are configured to pivotably couple to a surgical        instrument.    -   56. The assembly of any of claims 51 to 55, wherein the pair of        second recesses are configured to pivotably couple to a surgical        instrument.    -   57. The assembly of any of claims 51 to 56, wherein the U-shaped        recess is configured to receive a spinal fixation element of        various sizes.    -   58. The assembly of any of claims 51 to 57, wherein each spaced        apart arm has a laterally-facing recessed portion formed on        opposite lateral edges of the arm, each of the lateral-facing        recessed portions facing away from a central proximal-distal        axis of the receiver member, wherein the lateral-facing recessed        portions are configured to engage with a surgical instrument        such that the U-shaped recess remains unobstructed.    -   59. The assembly of claim 58, wherein each of the lateral-facing        recessed portions extend distally from the proximal end of the        spaced apart arms.    -   60. The assembly of claim 58, wherein each lateral-facing        recessed portion has a concave distal surface.    -   61. The assembly of claim 60, wherein each lateral-facing        recessed portion has a first planar surface, a second planar        surface substantially perpendicular to the first planar surface,        and a curved surface therebetween.    -   62. The assembly of any of claims 51 to 61, wherein opposing        laterally-facing sides of the receiver member taper inward        towards the proximal end of the receiver member.    -   63. The assembly of any of claims 51 to 61, wherein a first pair        of opposed sides of the receiver member has a first taper with        respect to a first plane that contains a proximal-distal axis of        the receiver member.    -   64. The assembly of claim 63, wherein a second pair of opposed        sides of the receiver member has a second taper with respect to        a second plane that contains the proximal-distal axis and is        offset from the first plane.    -   65. The assembly of claim 64, wherein the first plane is        perpendicular to the second plane.    -   66. The assembly of any of claims 51 to 65, further comprising a        drag ring disposed within the receiver member, the drag ring        configured to exert a friction force on the head portion of the        bone anchor.    -   67. The assembly of any of claims 51 to 66, further comprising a        compression member disposed within the receiver member, wherein        a proximal portion of the compression member includes opposing        planar surfaces that are angularly offset from one another        forming a seat for receiving a spinal fixation element.    -   68. The assembly of claim 67, wherein material displaced in the        formation of the second recesses is configured to restrict        movement of the compression member relative to the receiver        member.    -   69. The assembly of claim 67, wherein the displaced material is        received within corresponding recesses formed in the compression        member.    -   70. The assembly of any of claims 51 to 69, further comprising a        pair of reduction tabs extending proximally from the pair of        spaced apart arms.    -   71. The assembly of any of claims 51 to 70, further comprising a        fixation element with external square threads configured to be        received between the spaced apart arms of the receiver member.    -   72. The assembly of any of claims 51 to 71, wherein the bone        anchor includes a bore extending proximally from a distal tip of        the bone engaging portion.    -   73. The assembly of claim 72, wherein the bore extends through        an entire length of the bone anchor.    -   74. The assembly of claim 72, wherein the bore is a blind bore.    -   75. The assembly of any of claims 51 to 74, wherein the distal        bone-engaging portion further comprises external threads that        extend distally along the bone-engaging portion to a distal tip        thereof.    -   76. A bone anchor assembly, comprising:        -   a bone anchor having a proximal head portion, a distal            bone-engaging portion with external threads that extend to a            distal tip of bone anchor, and a bore centered within the            distal bone-engaging portion extending proximally from the            distal tip of the bone anchor; and        -   a receiver member having a proximal end defined by a pair of            spaced apart arms forming a U-shaped recess configured to            receive a spinal fixation element therebetween and a distal            end having a polyaxial seat formed therein for polyaxially            seating the head portion of the bone anchor.    -   77. The assembly of claim 76, wherein the receiver member        further comprises a groove formed in an outer surface of each of        the spaced apart arms at a proximal end thereof, a first recess        formed in the outer surface of each arm with at least a portion        of the first recess intersecting the groove, and a second recess        formed in an outer surface of the receiver member at a position        distal to the first recesses;        -   wherein the first recesses and the second recesses are            configured to couple to a surgical instrument.    -   78. The assembly of claim 77, wherein at least a portion of the        first recess in each arm extends proximally beyond the groove.    -   79. The assembly of claim 77 or 78, wherein each of the second        recesses is longitudinally aligned with one of the first        recesses.    -   80. The assembly of any of claims 77 to 79, wherein the first        recesses are configured to pivotably couple to a surgical        instrument.    -   81. The assembly of any of claims 77 to 80, wherein the pair of        second recesses are configured to pivotably couple to a surgical        instrument.    -   82. The assembly of any of claims 76 to 81, wherein the U-shaped        recess is configured to receive a spinal fixation element of        various sizes.    -   83. The assembly of any of claims 76 to 82, wherein each spaced        apart arm has a laterally-facing recessed portion formed on        opposite lateral edges of the arm, each of the lateral-facing        recessed portions facing away from a central proximal-distal        axis of the receiver member, wherein the lateral-facing recessed        portions are configured to engage with a surgical instrument        such that the U-shaped recess remains unobstructed.    -   84. The assembly of claim 83, wherein each of the lateral-facing        recessed portions extend distally from the proximal end of the        spaced apart arms.    -   85. The assembly of claim 83, wherein each lateral-facing        recessed portion has a concave distal surface.    -   86. The assembly of any of claims 76 to 85, wherein the proximal        ends of the spaced apart arms lie along a common circular        circumferential path.    -   87. The assembly of any of claims 76 to 86, wherein opposing        laterally-facing sides of the receiver member taper inward        towards the proximal end of the receiver member.    -   88. The assembly of any of claims 76 to 86, wherein a first pair        of opposed sides of the receiver member has a first taper with        respect to a first plane that contains a proximal-distal axis of        the receiver member.    -   89. The assembly of claim 88, wherein a second pair of opposed        sides of the receiver member has a second taper with respect to        a second plane that contains the proximal-distal axis and is        offset from the first plane.    -   90. The assembly of claim 89, wherein the first plane is        perpendicular to the second plane.    -   91. The assembly of any of claims 76 to 90, further comprising a        drag ring disposed within the receiver member, the drag ring        configured to exert a friction force on the head portion of the        bone anchor.    -   92. The assembly of any of claims 76 to 91, further comprising a        compression member disposed within the receiver member, wherein        a proximal portion of the compression member includes opposing        planar surfaces that are angularly offset from one another        forming a seat for receiving a spinal fixation element.    -   93. The assembly of claim 92, wherein material displaced in the        formation of the second recesses is configured to restrict        movement of the compression member relative to the receiver        member.    -   94. The assembly of claim 93, wherein the displaced material is        received within corresponding recesses formed in the compression        member.    -   95. The assembly of any of claims 76 to 94, further comprising a        pair of reduction tabs extending proximally from the pair of        spaced apart arms.    -   96. A bone anchor assembly, comprising:        -   a bone anchor having a proximal head portion, a distal            bone-engaging portion with external threads that extend to a            distal tip of the bone anchor, and a bore centered within            the distal bone-engaging portion extending proximally from            the distal tip of the bone anchor; and        -   a receiver member having a proximal end defined by a pair of            spaced apart arms forming a U-shaped recess therebetween, a            distal end having a polyaxial seat formed therein for            polyaxially seating the head portion of the bone anchor, a            groove formed in an outer surface of each of the spaced            apart arms at a proximal end thereof, a first recess formed            in the outer surface of each arm with at least a portion of            the first recess intersecting the groove, and a second            recess formed in an outer surface of the receiver member at            a position distal to the first recesses;        -   a drag ring disposed within the receiver member, the drag            ring configured to exert a friction force on the head            portion of the bone anchor; and        -   a compression member disposed within the receiver member,            wherein a proximal portion of the compression member            includes opposing planar surfaces that are angularly offset            from one another forming a seat for receiving a spinal            fixation element;        -   wherein the first recesses and the second recesses of the            receiver member are configured to couple to a surgical            instrument;        -   wherein each spaced apart arm has a laterally-facing            recessed portion formed on opposite lateral edges of the            arm, each of the lateral-facing recessed portions facing            away from a central proximal-distal axis of the receiver            member, wherein the lateral-facing recessed portions are            configured to engage with a surgical instrument such that            the U-shaped recess remains unobstructed;        -   wherein opposing laterally-facing sides of the receiver            member taper inward towards the proximal end of the receiver            member.    -   97. The assembly of claim 96, wherein the proximal ends of the        spaced apart arms lie along a common circular circumferential        path.    -   98. The assembly of any of claims 96 to 97, wherein the        compression member is locked against removal from an interior of        the receiver member.    -   99. A bone anchor assembly, comprising:        -   a bone anchor having a proximal portion and a distal            threaded bone-engaging portion;        -   a locking sphere configured to couple to the proximal            portion of the bone anchor;        -   a receiver member having a proximal end defined by a pair of            spaced apart arms forming a U-shaped recess therebetween,            and a distal end having a polyaxial seat formed therein for            polyaxially seating the locking sphere;        -   a drag ring disposed within the receiver member and            configured to exert a friction force on the locking sphere;            and        -   a compression member disposed within the receiver member;        -   wherein a distal facing surface of the receiver member is            obliquely angled relative to a central proximal-distal axis            of the receiver member to provide a greater degree of            angulation of the bone anchor relative to the receiver            member in a first direction relative to a second, opposite            direction.    -   100. The assembly of claim 99,        -   wherein the receiver member includes a groove formed in an            outer surface of each of the spaced apart arms at a proximal            end thereof;        -   wherein the receiver member includes a first recess formed            in the outer surface of each arm with at least a portion of            the first recess intersecting the groove, and a second            recess formed in an outer surface of the receiver member at            a position distal to the first recesses;        -   wherein the first and second recesses are configured to            couple to a surgical instrument.    -   101. The assembly of claim 100, wherein at least a portion of        the first recess in each arm extends proximally beyond the        groove.    -   102. The assembly of claim 100 or 101, wherein the second recess        is longitudinally aligned with one of the first recesses.    -   103. The assembly of any of claims 100 to 102, wherein the first        recesses are configured to pivotably couple to a surgical        instrument.    -   104. The assembly of any of claims 100 to 103, wherein the        second recess is configured to pivotably couple to a surgical        instrument.    -   105. The assembly of any of claims 99 to 104, wherein the        U-shaped recess is configured to receive a spinal fixation        element of various sizes.    -   106. The assembly of any of claims 99 to 105, wherein each        spaced apart arm has a laterally-facing recessed portion formed        on opposite lateral edges of the arm, each of the lateral-facing        recessed portions facing away from the central proximal-distal        axis of the receiver member, wherein the lateral-facing recessed        portions are configured to engage with a surgical instrument        such that the U-shaped recess remains unobstructed.    -   107. The assembly of claim 106, wherein each of the        lateral-facing recessed portions extend distally from the        proximal end of the spaced apart arms.    -   108. The assembly of claim 106, wherein each lateral-facing        recessed portion has a concave distal surface.    -   109. The assembly of claim 108, wherein each lateral-facing        recessed portion has a first planar surface, a second planar        surface substantially perpendicular to the first planar surface,        and a curved surface therebetween.    -   110. The assembly of any of claims 99 to 109, wherein the        proximal ends of the spaced apart arms lie along a common        circular circumferential path.    -   111. The assembly of any of claims 99 to 110, wherein opposing        laterally-facing sides of the receiver member taper inward        towards the proximal end of the receiver member.    -   112. The assembly of any of claims 99 to 111, wherein a first        pair of opposed sides of the receiver member has a first taper        with respect to a first plane that contains a proximal-distal        axis of the receiver member.    -   113. The assembly of claim 112, wherein a second pair of opposed        sides of the receiver member has a second taper with respect to        a second plane that contains the proximal-distal axis and is        offset from the first plane.    -   114. The assembly of claim 113, wherein the first plane is        perpendicular to the second plane.    -   115. The assembly of any of claims 99 to 114, wherein a proximal        portion of the compression member includes opposing planar        surfaces that are angularly offset from one another forming a        seat for receiving a spinal fixation element.    -   116. The assembly of claim 115, wherein material displaced in        the formation of the second recess is configured to restrict        movement of the compression member relative to the receiver        member.    -   117. The assembly of claim 116, wherein the displaced material        is received within a corresponding recess formed in the        compression member.    -   118. The assembly of any of claims 99 to 117, further comprising        a pair of reduction tabs extending proximally from the pair of        spaced apart arms.    -   119. The assembly of any of claims 99 to 118, further comprising        a fixation element with external square threads configured to be        received between the spaced apart arms of the receiver member.    -   120. The assembly of any of claims 99 to 119, wherein the bone        anchor includes a bore extending proximally from a distal tip of        the bone engaging portion.    -   121. The assembly of claim 120, wherein the bore extends through        an entire length of the bone anchor.    -   122. The assembly of claim 121, wherein the bone anchor includes        at least one outlet formed in a lateral surface thereof that        intersects with the bore.    -   123. The assembly of claim 120, wherein the bore is a blind        bore.    -   124. The assembly of any of claims 99 to 123, wherein the distal        bone-engaging portion further comprises external threads that        extend distally along the bone-engaging portion to a distal tip        thereof.    -   125. The assembly of any of claims 99 to 124, wherein the        compression member is configured to exert a force on the locking        sphere upon distal advancement of the compression member        relative to the receiver member.    -   126. The assembly of any of claims 99 to 125, wherein the bone        anchor includes threads of a first pitch formed along a first        bone-engaging portion thereof and threads of a second pitch        formed along a second bone-engaging portion that is proximal of        the first bone engaging portion.    -   127. The assembly of claim 126, wherein the first pitch is        greater than the second pitch.    -   128. The assembly of any of claims 99 to 127,        -   wherein the bone anchor includes threads formed on a first,            distal portion thereof and a second portion without threads            that is disposed between the first portion and the proximal            portion of the bone anchor;        -   wherein a length of the second portion without threads is at            least about 30% of a length of the first portion having            threads formed thereon.    -   129. The assembly of claim 128, wherein the length of the second        portion is between about 30% and about 90% of the length of the        first portion.

1.-98. (canceled)
 99. A bone anchor assembly, comprising: a bone anchorhaving a proximal portion and a distal threaded bone-engaging portion; alocking sphere configured to couple to the proximal portion of the boneanchor; a receiver member having a proximal end defined by a pair ofspaced apart arms forming a U-shaped recess therebetween, and a distalend having a polyaxial seat formed therein for polyaxially seating thelocking sphere; a drag ring disposed within the receiver member andconfigured to exert a friction force on the locking sphere; and acompression member disposed within the receiver member; wherein a distalfacing surface of the receiver member is obliquely angled relative to acentral proximal-distal axis of the receiver member to provide a greaterdegree of angulation of the bone anchor relative to the receiver memberin a first direction relative to a second, opposite direction.
 100. Theassembly of claim 99, wherein the receiver member includes a grooveformed in an outer surface of each of the spaced apart arms at aproximal end thereof; wherein the receiver member includes a firstrecess formed in the outer surface of each arm with at least a portionof the first recess intersecting the groove, and a second recess formedin an outer surface of the receiver member at a position distal to thefirst recesses; wherein the first and second recesses are configured tocouple to a surgical instrument.
 101. The assembly of claim 100, whereinat least a portion of the first recess in each arm extends proximallybeyond the groove.
 102. The assembly of claim 100, wherein the secondrecess is longitudinally aligned with one of the first recesses. 103.The assembly of claim 100, wherein the first recesses are configured topivotably couple to a surgical instrument.
 104. The assembly of claim100, wherein the second recess is configured to pivotably couple to asurgical instrument.
 105. The assembly of claim 99, wherein the U-shapedrecess is configured to receive a spinal fixation element of varioussizes.
 106. The assembly of claim 99, wherein each spaced apart arm hasa laterally-facing recessed portion formed on opposite lateral edges ofthe arm, each of the lateral-facing recessed portions facing away fromthe central proximal-distal axis of the receiver member, wherein thelateral-facing recessed portions are configured to engage with asurgical instrument such that the U-shaped recess remains unobstructed.107. The assembly of claim 106, wherein each of the lateral-facingrecessed portions extend distally from the proximal end of the spacedapart arms.
 108. The assembly of claim 106, wherein each lateral-facingrecessed portion has a concave distal surface.
 109. The assembly ofclaim 108, wherein each lateral-facing recessed portion has a firstplanar surface, a second planar surface substantially perpendicular tothe first planar surface, and a curved surface therebetween.
 110. Theassembly of claim 99, wherein the proximal ends of the spaced apart armslie along a common circular circumferential path.
 111. The assembly ofclaim 99, wherein opposing laterally-facing sides of the receiver membertaper inward towards the proximal end of the receiver member.
 112. Theassembly of claim 99, wherein a first pair of opposed sides of thereceiver member has a first taper with respect to a first plane thatcontains a proximal-distal axis of the receiver member.
 113. Theassembly of claim 112, wherein a second pair of opposed sides of thereceiver member has a second taper with respect to a second plane thatcontains the proximal-distal axis and is offset from the first plane.114. The assembly of claim 113, wherein the first plane is perpendicularto the second plane.
 115. The assembly of claim 99, wherein a proximalportion of the compression member includes opposing planar surfaces thatare angularly offset from one another forming a seat for receiving aspinal fixation element.
 116. The assembly of claim 115, whereinmaterial displaced in the formation of the second recess is configuredto restrict movement of the compression member relative to the receivermember.
 117. The assembly of claim 116, wherein the displaced materialis received within a corresponding recess formed in the compressionmember.
 118. The assembly of claim 99, further comprising a pair ofreduction tabs extending proximally from the pair of spaced apart arms.119. The assembly of claim 99, further comprising a fixation elementwith external square threads configured to be received between thespaced apart arms of the receiver member.
 120. The assembly of claim 99,wherein the bone anchor includes a bore extending proximally from adistal tip of the bone engaging portion.
 121. The assembly of claim 120,wherein the bore extends through an entire length of the bone anchor.122. The assembly of claim 121, wherein the bone anchor includes atleast one outlet formed in a lateral surface thereof that intersectswith the bore.
 123. The assembly of claim 120, wherein the bore is ablind bore.
 124. The assembly of claim 99, wherein the distalbone-engaging portion further comprises external threads that extenddistally along the bone-engaging portion to a distal tip thereof. 125.The assembly of claim 99, wherein the compression member is configuredto exert a force on the locking sphere upon distal advancement of thecompression member relative to the receiver member.
 126. The assembly ofclaim 99, wherein the bone anchor includes threads of a first pitchformed along a first bone-engaging portion thereof and threads of asecond pitch formed along a second bone-engaging portion that isproximal of the first bone engaging portion.
 127. The assembly of claim126, wherein the first pitch is greater than the second pitch.
 128. Theassembly of claim 99, wherein the bone anchor includes threads formed ona first, distal portion thereof and a second portion without threadsthat is disposed between the first portion and the proximal portion ofthe bone anchor; wherein a length of the second portion without threadsis at least about 30% of a length of the first portion having threadsformed thereon.
 129. The assembly of claim 128, wherein the length ofthe second portion is between about 30% and about 90% of the length ofthe first portion.